Hi BillS,

After doing some research on the engines that I have available, there is very little difference between the 2 engines in HP and maximum RPMs. Both will do 16k max rpm, and the 61 has a .5 HP advantage over the 50. I'll then probably go with the .50 in order to save the additional weight of 12.47 ozs. I'll be trying an APC 11x6p for the initial flight, and then an APC 10x7p to see which gives better performance. As it is, even with my battery pack located right in front of the fuel tank, it still balances a little nose heavy (about 9.5" from the leading edge). It should be interesting to see how she handles. The 50 with a pipe should be able to push max revs, which should be better than the 61. I fly off a cement surface, so she should be able to get up to speed without any problems. I'll let you know how it turns out. Happy Flying!