We have run a standard box this year and had no problem at all,in fact we have never got into 5th.Next year we will be running with a different final drive to make use of 5th.Going to see what happens at Snetterton this weekend ie,if we hit the limiter in 4th down the back straight,if so for how long for so we can work it out.Castle Coombe,Silverstone and Anglesea we just hit limit before we lift off for a bend so not a problem.LSD we don't run as it just complicates things if anything goes wrong gearbox wise.