I have a Poulan 25cc weedeater conversion going, I have a Frank Bowman ring in the works for it but I was hoping someone with more conversion experience could also help.

In this engine @ TDC the piston is .025" away from the top of the jug. I could shorten the jug by .005" so the piston would be that much higher in the jug.

Would it be worth the trouble? . I have verified with my depth micrometer set that I can reduce the gap at TDC to .015" and still have no interference from the spark plug as the top of the jug is hemispherical. But would this also change the port timing?

Just an idea, I have 5 of these engines so I'm not that worried about experimenting some.