Hey,
I've always heard an inch or two is good for road bike sizing. This is the amount of clearance I have on my road bike. I tend to like larger frames for some reason, and favor a slightly larger size, so I usually run a little less clearance than others who I mountain bike with. I tend to think 5 inches or so is excessive depending on what type of MTB'ing you are doing, though many people fit an MTB that way. The general guidelines above are correct from what I have heard. I'd say you are ok if you will be using the bike on the road for the most part. If you might decide to try the offroad route more often though, you should probably consider a slightly smaller frame.
-Moab
EDIT: Was typing this when Justen posted preiously.