I had a Moki 1.35 in a .60 Do, beefed up firewall and gear mounts & flew fine. A OS 1.08 or new 1.20FX 2 stroke is great for the .60 Do. Have flown w/ OS 1.08 for many years, I use a Zinger 17X5 prop. Use 4/40 push rod or CF over 4/40, with tight linkages(DuBro ball links are best) there will be no flutter which can seem to "explode" a plane at WOT straight runs. I still have one, but due to 50cc class 3-D planes, the Do is getting hanger rash. I have offers up to $50 to bring it out so they can burn it, go figure??!! I could do almost every 3-D maneuver with it.