I picked up a used webra 40 blackhead a while back finally mounted it ln a 40 sized high wing trainer and fired it up. This engine seems faster than my webra 40 silverline. my question is to which propsize should I start with on the ground it seems to swing a 10-6 very fast but maby it should. I reailize this plane would be better off with a bushing 40 but this is is what I have and I do not want to spend any more money than I need to on it.

Thanks.