Well I'm baffled. Just what adjusments are you planning on making that can't be done from behind the prop? There are ways to have a deliberate shaft run that were used long ago to run in things like Dooling .61's but it's probably best not to mention them here or the field nazis will have a ball

I wouldn't try a shaft run with a 4 stroke though because those valves will float like crazy and get bounced around by the piston.