I am surprised you are running out of gear with a 3.73 and 7k in avialable revs. Are you running 15" wheels?

I've never driven Summit, but the front straight doesn't appear to be longer than VIR's back straight. Top speed there is about 128-130 for a good R or S car, maybe a bit more.

Wheels are cheap gearing. You can run 17s" in R right? You might want to try that first, although again, very surprised you are out of gear at Summit with a 3.73. I run a 3.45 in my car, with 15" wheels and 225/45 R6s. With a .82 or something 5th I'm not even close.

Of course, I jsut remembered -- you guys have a 1:1 Fifth gear don't you?