If you're going to throw that much extra metal on the end of a plastic body I would suggest
Madbull's RAS FIX Scope Riser Mount. It connects the top rail of the upper reciever with the RAS just beyond the delta ring. Helps to reduce the amount of barrel wobble associated with plastic M4 bodies. With a rail system that long on your SR-16 it may create even more stress than the stock TM RIS.
Of course, if you're already running a metal body then it shouldn't be a problem
