Well, the temptation is to ignore all you wrote and tell you to get a high quality hood, at least 54'' wide, ideally 27'' deep, with a remote blower rated at least 1200 cfm.

But, if I can get past my personal biases on this subject, I'd say this: a 48'' hood is not optimal, but it's not disastrous either. Indeed, if you have cabinets on either side of the hood as it sounds, there's even some compensation, as the cabinets will to some degree reduce the lateral drift of the fumes etc, compensating partially for the inadequate hood width.

I would put in a plea to at least consider a remote blower. How will your ductwork exit the house? If there is the opportunity to do a remote blower, I'd still consider it as I think it makes a huge difference.

I don't offhand know the burner configuration of the BS you are ordering. What's the total BTU output of all burners plus griddle? That would help to know if the 900 cfm spec is adequate.

What kind of "look" are you going for?

More info please!

The grill and griddle are located in the center of the range, this location helps. You have not indicated the design of the duct run? Is it straight out the back, is it straight up, are there elbows, how many elbows. What is the maximum size duct you can run 8", 10"? What height is the hood going to be off the cooking surface?

900 CFM is definitely not recommended for that range. You are talking about a lot of BTU's there 1200 should be the lowest you should go. Internal or External dooesn't matter nearly as much as duct run length and the type of hood used. At least use one with baffle filters if not a ventahood style filterless hood system

Absolutely you must at least go with a 1200 CFM configuration. Bluestar makes there own hoods so that would be a great option. Baffle filters was a great reccomendation joboxes and they come standard with all BS hoods.

I understand that the OP does not want to do this, but I will point out that one disadvantage of the BS hoods is that they appear to come exclusively with internal blowers. If you're really looking to do a superior ventilation install, then a remote blower has substantial advantages, especially when you're considering very high flow blowers. I know I am glad I don't have a 1200 cfm blower mounted a foot and a half away from my ears when I'm cooking.

In my somewhat limited experience it appears to me that the ventilation systems sold by the stove mfg., under their brand name, are usually not of the best quality,noisy and over priced. You most definitely want an internal blower with a muffler/silencer.

Make that inline centrifugal fan. Fantech 10xl is excellent.

Just keep in mind that if your hood doesn't capture your cooking fumes on the first pass they are going to mix with all the other air in the living structure. Once that happens the blower actually needs to exchange all the air in the structure several times because it keeps mixing with the new air coming in, and in the mean time any aromas from frying are going to be carried by microscopic oil droplets (which don't evaporate by the way) until they cling to upholstery, carpets, window treatments and bedding. That's fine if you like sleeping on a garlic scented pillow, but most people don't, and also if the air outside is a perfect 72 degrees F and you don't have to heat or cool it when you bring it in. You need twice the normal sized blower in a hood application to create enough flow to compensate for an undersized opening. That normally means that you should have a make-up air system installed to prevent negative pressure conditions in the house. An appropriately sized hood extending 3" over that cooktop and the smaller blower will pay for themselves a thousand times over.

I'm pleased with the KOBE CH-100 over my 48" BlueStar. It uses a 4 speed two internal motors with max output of 1000 cfm, utilizing a baffle type filter system. I use the "Quiet Mode" most often. However, infrequently, I would like another 200 extra cfm when using high BTU's with stir-frying. As others have said, get your blowers going a minute before your food hits the "fire". I have a straight duct configuration and cabinets on both sides of hood.
Ultimately, for me, my choice came down to compromises. I wanted the warming lights and halogen spot lights, where most hood manufacturers offer one or the other, at an affordable price. My SIL uses a VAH hood over their 48" Thermador. It is not as quiet on it's low speed, but quieter on it's high speed compared to the KOBE. Also, costs alot more. Good luck and enjoy the process.

annettesdh makes some interesting points if I'm reading him correctly. First point is certainly on target: inadequate capture area means a significant proportion of cooking vapors will not be captured, and then they travel merrily around your house.

I don't believe however that no matter how large the blower is sized, that it will ultimately do any significant "recapture" of fumes that have escaped the hood. It's true that if you look at it the way we look at bathroom vent fans, which are typically rated by how many times per hour the fan will exchange the entire volume of air in the bath, that you could argue that high flow ventilation will eventually exchange all the air in the kitchen, removing those fumes. I think there are flaws in this reasoning. First, kitchens are rarely small, closed off spaces the way bathrooms are. The likelihood is that escaped fumes will travel far outside the kitchen well before they are vented out the hood (annettesdh actually makes that point by referring to odors in bedrooms, living rooms etc). There's no way that any kitchen blower of any size will pull all the air back out of the bedroom and living room once they've escaped. Cooking also tends to continuously produce more effluent, whereas bathroom ventilation is generally for steam and odor produced over short periods of time, allowing for better capture.

I didn't follow the point about 72 degree air outside.

I'm unaware of any reference source that supports the arbitrary notion that doubling the blower capacity makes up for an undersized hood. Way too many variables there to make any generalization I believe.

Weissman and I have debated make up air many times. I'm still not convinced that, outside of code and very cold climates, it's really needed unless you have an extremely tight house.

But, agree with overall conclusion that bigger capture area and lower blower rating are better than the opposite (though I still favor our approach, bigger capture area AND bigger blower rating!).

clinresga - I think we're basically in agreement on everything here.

The mention of 72 degree outside air was just to make the point that air going through the exhaust hood is ultimately being drawn into the house from outside and must therefore be heated or cooled...which uses more energy.

My guess is that most people will keep running their hood until they at least clear visible smoke out of their kitchen. That's not what it's designed for, but you're right, fumes will actually go everywhere. Once they mix with air outside the stove/hood area you can only reduce them not eliminate them.

I have to admit that even doubling the cfm is no guarantee of capturing passing fumes with an undersized hood. It could also be less than that in a given situation. Not worth the risk.

dh: yup, I think we're on the same page. good points.