Hey Corey,

First, I don't know much about the GMS motors but that is right were the 25FX and Norvel motors run stock with a old style MAS 9x4.
The new style MAS they call a G/F 3 Series has a wider blade and runs a little slower on my motors. I normaly put locktite on all screws and nuts and RTV on the backplate and the carb to case joint. More ntiro generally means more speed but I think most guys run 15% and if the muffler has a internal baffel of some type taking it out will help. Here's some pics. If you make one the rules say the overall length can't be more then 8 inches. I think 18k is about the middle ground, there'll be some a little faster, some a little slower but keep in mind the fastest plane rarely wins. Have you decided to come to the contest for sure?

Mousse Can Write Up
http://www.georgiacombat.com/KYMousseCan.html

Rick