Yeah, Locking the Diff is a good Idea but I would onlydo that after you have got basic Car control..

Locking the rear Diff will make the Car Tail happy.. Basic Car control will be needed prior to locking the rear diff so you can keep it in a straight line when needed...

Wack some ABS/PVC Tyres onto a fresh set of rims, practice Sliding it, then if You find it isn't drifting the way you want it to, Lock the rear Diff with Blu-Tac.

My HBX Drifts fine Stock.. So I haven't found the Need to lock the diff, so If I wanna race on rubber, I can just change the Rims and Tyres and go for it...