Ok got some on order to try, Also couple quarts of lower Nitro, ya know it's spring I just gotta play.

BUT !! help me on this new problem if I under prop it where is the danger rpm, 11600 on pattern 9-7 now can this old boy ROYAL 28 take high 13,000 15,000 or OMG 18,000 or will I just ruin this engine.

I don't know if royal is a classic or not just hate to take it out trying to do something it's never done or will do but once.[]

BTW putting it on our club racer to practice on then switch over to Tunder Tiger 25 the legal one. Royal was the motor until discontinued, they then went to TT but now it's dissappearing wow what a sport.
Rich