Captain,

Oh wait, I see what you mean. Adjust the compression while the engine is running. I've done that, (on glow at least) on a Norvel .15. That revealed that the .15 and possibly the .25 and the .40 are undercompressed.

See,

http://www.youtube.com/watch?v=_pN6-rgXEFk

Something to consider doing with the Tanaka.

OK, that makes four heads to make. Got to stock up on some large diameter aluminum bar. [X(]