I have had my gbox rebuilt a number of times at cts
I had it built just before i did another track day ,
It wasnt good coming into a corner not being able to select the correct gear,
I have a lightweight tripple clutch which mark pointed out you need for high rev gear changes
There was also a bad vibration through the car which i suspect is the box which i think may have been one of the factors of my engines demise,
Im going to be looking at the tremec i know real steel do them as does Martin
I think this could be the way forward ,
I know a lot of 10 sec american drag cars use them and there cars arnt exactly light weight the only concern i have is that there bolted to relativley low reving v engines
and as Dingy has commented would the box be anygood on the back of a high rever on track ???