NEED some ideas!! Seeking to UPGRADE a stock (and as yet UNBUILT) Estes Patriot to use BOTH the stock 18mm motors AND 24mm motors (bigger C's, D's, and maybe E's). a.) Have read that Estes rocket power recommendations are conservative. b.) Wish to LEARN the various techniques required for the transition from LPR to MPR... thought this model might be a good candidate. Should I use TTW fins? MMT length required for a 24mm motors? Fiber board OR Ply CRs? My MAC WILL NOT download ROCKSIM!! Tried EVERYTHING...including TRF self-help and directives as well as ONLINE searches to get this program on my computer!! Planning to scratch build an Estes Leviathan... already have the 29mm MMT, 3" rocket tubing, nose cone, downloaded and have printed a patterned 1/8" plywood FIN design. Also ordered and received the material to scratch build a SCION. OH! My North Coast Rocketry SA-14 Archer should be at the door next week!! The Estes Patriot is on the build board with the Excalibur coming up next....then the Leviathan and Scion builds after this. Thank you!