+1 to all that...I run a 7mm venturi in both my MM5 3 and 7 ports.The power loss isn't noticeable really just smooths it out a bit but the longer run times are cool..The shim can stay in for 30% nitro but I only ever run 20 or 25% and after 2 gallons I remove the xtra shim and change the rod and wrist pin and clips all at the same time..I don't see the need for 30%..I found the power increase to be negligible but the engine & plug life are shortened and I found the engine to be much less tolerant of being a bit lean on the mixtures..I killed one engine real quick with a can of 33%..