mgang- It was recommended to me to get an exhaust slightly larger than my stovetop. I think the general rule is 2-4 inches overlap on both sides...

Agreed with musicgal. BAD IDEA to go under 48" and if anything you should get 54". Remember, function over form. However if you don't like the look of a big giant stainless hood you can get an insert.

I imagine your concern in a small kitchen is the loss of storage in wall cabs as well as the visual dominance of a 54" hood.
Here's a suggestion that will somewhat ease both of these concerns:
Choose a hood that looks more or less like this 36" ModernAire (but wider, of course!):

Then have your cabinet makers continue your cabinet run above the hood, like this:

Above is my ModernAire hood with cabinets closed. Below are the same cabs open. I store seldom used items here--this is most of a vintage china serving for more than 12 that belonged to my parents. (I seldom, but occasionally--like once a year--serve more than eight people, so this works perfectly.)

Because my hood vents straight out the wall behind, the pipe does not extend upwards beyond the motor housing. It may need to run to the ceiling inside your cabinets. Of course, in your much wider hood (mine is only 36"), you will have far more storage on each side of the housing and pipe.

If this look works in your kitchen, I urge you to consider it, rather than installing a too-small hood that will not do what you need it to do. Yes, you'll lose the storage space that would have been under the narrower hood (but only that), but you'll gain the exhaust pick up you will truly need.

One caveat if you consider this: this motor housing barely fits in my 15" deep wall cabs. If you have 12" wall cabs, the cabinet maker can bump out the framing around the vertical pipe if necessary.

This post was edited by Bellsmom on Fri, Aug 15, 14 at 11:36

*Nice* setup bellsmom!

Adding to the good advice given above, I'd suggest that you search the many hood discussions here and I especially recommend posts by kaseki. You will find that what you are considering is actually counterproductive to your goals. To summarize briefly:

First, if you are putting cabinets over that 48" range top, read the installation manual for your rangetop. On most rangetops, cooktops and ranges, the manual will specify that bases of the upper cabinets should be at least 30 inches above the stove top. IIRC, some even specify 36". Going lower is considered a fire hazard. Thus, you really can't gain cabinet space over a 48" range/rangetop by using a smaller hood.

Second, the effectiveness of ventilation hoods has as much or more to do with hood "capture area" as blower power. If you want to try to make up for poor capture, you need a huge increase in blower force. Think about using a vacuum cleaner. The stronger the blower, the more noise the system will make as you try to suck everything in -- maybe sucking pets and and small children off the floor :>) --- and a very loud roar. Same thing if you put a powerful vent fan in the ceiling. That kind of power utterly defeats your desire for a quiet hood.

Third, a huge step-up in blower power means a huge step up in the need for make-up air, and that can and likely will be a major expense. Doesn't matter if your locality does not have codes that require MUA. We're talking the laws of physics here and avoiding backdrafting HVAC, water heaters, fireplaces, etc.

Fourth, while a properly sized and designed hood may be larger than you seem to like, it also can be a lot quieter. Consider that there are two sources of noise in hoods: (a) the noise of the fans and their motors and (b) the air rushing through the baffles/filters and into the ducts. With a properly sized hood, the fans can run lower and slower because the hood enables the capture. Slower fans are quieter.

If you have cabinets on both sides of the hood that are flush with the hood, you can get away with a hood the same width as the cooktop. Like that first picture. If the cabinets are not flush with the hood, then the hood needs to be wider.

What's the layout of your 48 incher? Unless both of the middle rows is taken up by grill and/or griddle then I'd argue that for most cooks the "dirty" pot/pan cooking will be done in one of the two middle columns, simmering and stuff on the outer burners. If that's your expectation then I think a 48" hood is fine, even if a 54" would be theoretically ideal.

That said, please explain your desire for something narrower than 48"? IMO it'll look awkwardly undersized, but moreover, what are you gaining? I certainly hope you're not trying to extend your upper cabinets over the burners???