Got a nitro t-15 hpi the head button gone.:mad got spare head fits ok have no shims so orderd one but the top ov the slev and the engine were the head seats thars a 1-2ml gap the head i got has half a ml drop in the engine when it sits ready to be bolted on when the shim comes hope its thik anoth. Does any one done this before???as this is new to me dont know if it will work hope so.???????????????