Mike, do yourself a favor, do not spend $200 into henglong and get not eve 10% of perfection of tamiya. I have done a all modification including gun recoil, turret rotation, gun elevation with ESCs but that will be lots of work and money. then the result is no sound, no light. and not acurate.
if you made up your mind on modifying HL, pm me, I will give you my phone, so we can talk over the phone, it is too long to type all modification u need.
tom