I am currently using both rooms, and as of my first BEO, I was $200 under the combined minimum. My WC said we wouldn't loose the room, but we would be charged the minimum. No exceptions. I wasn't worried because we low-balled our guest count, and I'm going to be fine because we have more guests than we originally guests. So, I don't have a low guest count per say, but I do have some ideas on how to spend your money
$1500 seems like a lot to spend on drinks - but you know your guests. The bar menu can be found
here if you want to take a look.
Today my WC sent me the new 2010 menus and there was a new (well at least to me) thing called enhancements. These are little take away favors and center pieces (edible so they would count toward your f&b minimum) you can check those out
here I think they're way cute! And that could help too.
Also, have you can add appetizers for the pre-reception.
...and.... have you thought about the Sonoma Room? It's right across the hall from the Napa Room, but it's smaller with a $2,000 F&B min. after 5. The view is of Bay lake, but you still have the use of the catwalks. That could save you from stuffing your guests and forcing drinks on them just to spend money