I do have a Hanno Special, a 61VF and a YS61R to choose from although the low weight and simplicity of the 55AX really appeals to me. I have a 55AX with Macs long header and Hatori pipe in an ARF Curare and it flies great. More than enough power with the header uncut running 15% nitro with a 12x7 apc prop. But the Calypso may end up half a pound or so heavier than the Curare that's why I am concerned. I will probably give it a try though and just lighten the Calypso as much as I can.