I have diamond dust with an os 32 with a pre tuned MACS pipe.
Can I shorten the pipe and get more rpms? If so, how much should I shorten it? What are the drawbacks to haveing too short a pipe? Tuning, engine life?

Here is something that has me wondering if the engine will go any faster.

I had a APC 8x8 and got 17,100 rpm on the ground with 15% fuel. I tried a 8x9 with 15% and had about 15,900 rpm.
I tried 30% fuel on the 8x8 and got about 17,000. I went a head and tried the APC 8x9 on 30% and got 16,900rpm. It seems like the engine was making more power but I couldn't get any more rpms. The 8x9 really moves the plane well.

You should have seen this engine and pipe on a .10 shrike. It was really screaming just before the wing came off.

Harlan