If you look at the Modern-Aire site, they have several shapes where the front tapers at the top to the depth of an upper cabinet, and the sides are straight so as to butt up to, and cover, the yellow cabinet sides you mentioned. Their typical sizes are 18" and 30" high, but you could get a 24" custom one if your budget allows. Or you could get an 18" and have a box made for above it to cover that area and to which you could attach replacement moulding. The box could be made of either wood matching your moulding or sheetrock. Vent-a-hood has a stainless direct replacement if you decide to stick with the same size you now have. I'm attaching the link to the Modern-Aire page that shows their shapes. PS-10, PS-11, and PS-26 all have the characteristics I was talking about above. Here is a link that might be useful: Modern-Aire Hoods

@sarina: I have had the Kobe RA02 for about 8 months now. Being an engineer, I did the install myself, although the chimney cover is still not in place, as I need to redo the crown molding behind it (procrastination is the name of this game). Overall I like it, but that doesn't say much, as my previous ventilation was just a fan-in-a-ceiling-hole. The quiet setting is quiet, but the other two are noisy; without previous experience, the "sones" numbers don't translate well into actual noise levels. Otherwise, on High, the hood is pulling out all the smoke and airborne grease steaks in a cast-iron skillet produce. You will have to open a window or install a MUA to help it pull all that air volume. The baffles need scrubbing every month or so, but that's a very small price to pay for not having cabinetry and walls smeared in grease. The model you're looking at is a little more elaborate, as it has some sort of electronic control. The RA02 is bare-bones, just two rotary switches.

First of all, thank you everyone for taking the time to address my issue. So per suggestions from the post, i increased the hole size in the cabinet and was finally able to attach the hood to the cabinet with all screws in. As the new hole size is approximately 8 inches, so i bought a 8 inch to 6 inch duct reducer. Now my problem is that the if i try connect one 6 inch adjustable elbow with the 8-6 inch reducer.. it is just short (they don't connect) - Shown in the picture and if i were to use 2 adjustable elbows then the part of hole in the cabinet will remain exposed.. I am not sure, What are my options? can i buy one 6 inch piece somewhere, what is it called? Any suggestions or thoughts are much appreciated. Thanks

I guess it's done per the comment above?? I was wondering about cracking too! I see photos all the time of what looks like one large tile slab w/ a wall mounted range hood on it, but wasn't sure. Thanks both of you + have a nice weekend!:)