A 600 class, is something such as a graupner speed 600, great planes uses them to i think, i believe its comparible to a 540 size almost the same maybe, correct me if im wrong cuz im not sure, I run two BL, high end to power that beast, even small gyros are hard to push with small motors, I have a G3po i dont used right now, needs rebuilt again, cause my bl wouldnt pull it, and it was around 10-12 ounces, and i have around 16 ounces of thrust, to give you an idea, also it comfortablly swings a 10-3.8 prop or a 9-3.8 which i prefer for more RPM and better effiency with similar thrust. Id look into to big himax motor or axi's but then you need to escs(ouch my wallet crys thinking about that king of thing.