As Adam said mate you will pop the box if yuo just lob a stock one in. Give Bernie a shout at CTS and he'll sort you out. Price for a stage one box is very reasonable and you won't be whipping it out to replace it again after 5 minutes.

I also wouldn't lose the RS's LSD. You'll only spin the wheels more and the car won't drive as well either. Despite what some people may tell you the Diesel box is no tougher than any other box the ratios are taller which mean the car will be slower sprinting.