I'm definitely no expert, but when I type in "bosch chimney hood" on Houzz, it seems that they are all the same size as the cooktops. All of the fancy wood hoods are usually done larger than the cooktop, but I guess these aren't.

Our designer recommended to us to have the hood slightly larger that our rangetop.

Cooking by products spread upwards and outwards in V shape. If you are to capture all of them and not have nasty grease on your nice new cabinets, then you need a hood that is both wider and deeper than the cooktop below. And with a concave shape to capture the byproducts, and sufficient fan and makeup air to get them out of the house.

If you have cabinets abutting the hood, you can use a 30" hood without any problem. I've had that setup with a pro-style range for 11 years and the side cabinets never get greasy. On the other, getting a deep hood is important - mine doesn't cover the front burners completely an I do end up with grease on the outside front of the hood.

My research taught me that in a perfect world the hood should be 6" larger...3" per side. Better for capture.

Thank you, Guess it will be 36" for sure.

Thanks again!