I've had the Sundancer in the air since July 2006. I fly in the altitude 6200 ft. I have a Irvine .61 in mine, swinging a APC 12x6. It's just enough power for the altitude loss. Not unlimited vertical, but good power. See my review on RCU. I starting swinging a 13x6, not quite enough rpms. I went to a 12x6, much better. I generally beef up the construction on all my ARF's. This plane came in exactly 1 pound over weight (7 lbs). This is a great plane! Flies great, performs great, lands even better..... She floats in like a trainer. I haven't tried it with the engines you are suggesting and haven't had any other experience with them. You might want to try what I did and not mount the engine inverted for ease of starting & so on. Experiment with the fit like I did and make your own choice. I hope this helps anyway?