I suppose I can try lowering the shim stack even further. I can only remove one more shim, though. Is it safe to run 0.2mm of shims on a .12 engine running on 30% nitro?

Also, am I correct in my assumption that switching back to the stock carburetor, with its narrower inlet, would reduce the top speed of the engine? I can't think of any reason why it would help, but maybe there's some detail I'm failing to consider.