If your entire hood starts to rumble, it is likely that the hood is vibrating at a resonance frequency. Check to see if the motor mounts are loose, otherwise you could have a bad blower shaft bearing that is allowing the motor to vibrate at a resonance at low speeds. Check to ensure all mounting screws/bolts are tight first. Good luck! Here is a link that might be useful: shoreview homes for sale

We only rarely run the fan at above medium. We only do that when we are cooking something that is very smoky. That is why I'm trying to figure out if there is enough bang for the buck or if we should just leave it alone and save the expense and trouble. John

a canopy is a collector volume. that is all. period. full stop. one does not void a warranty of a shape, for a shape being a shape. then, any blower blows air out the exit. or, the blower pulls air (if it's an inline blower). you can put the air exit where you want. if you buy an entire kit with the blower motor inside the canopy as part of the product kit, the question gets more complex but not by much. If you buy the kit, you will have spent a lot of extra money. This is counter intuitive. Here is a situation where the blower costs less if you buy it as a blower alone, and the canopy costs less if you fold some metal and call it good, or buy (as spare parts) a ready made shape but not the entire product. Hope this answers "I am curious if anyone has modified one of Viking's canopy hoods to vent straight out the back?" I'm not going to go check out a specific model in order to describe how i would shape the corners of the turns. (It's idle thinking).

Hoping for some advice so I am bumping this up.