A carefully balanced prop has reduced vibration to a comfortable-as opposed to an unnoticeable-level in this case Jack. I think the deliberately unbalanced prop approach (I have tried it) works better on the larger long stroke vintage diesels with relatively heavy pistons. Then there is the simple and well recorded reality that some engines have 'vibration bands' corresponding to a few thousand rpm or so somewhere in their rpm range. Within this they vibrate badly-propped above or below this band they run smoothly. Then there is the utterly counter-intuitive observation that some engines where there is no attempt whatsoever at any form of counter balancing-and with heavy pistons to boot-run quite smoothly-I give you the ED Bee, Elfin 149, DC Spitfire and Sabre and the Frog 100/149/150s as examples. Go figure...........!

ChrisM
'ffkiwi'