Verdict is in, the Gemini II 120 is out. I got the rig out last night and hung the bones of the Liberty Sport on it with the engine in place. It would take at least 7 ounces of tail weight to get it balanced, and that is with the battery and servos as far back as possible.
So I went through my stash, and pulled the 100 off the Cub and hung it on there. The balance came out really good with zero dead weight, so it looked like a viable candidate. It felt sticky and rough, so tore it down and found the front bearing needs to be replaced. The inner one is silky smooth. Is the OEM bearing steel shielded on both sides? I found two small dents on one side, so I question if these were replaced.
So I go through all this and then check the mounting location and length. Should have done that first before spending all that time tearing it down, it's too long. The Gemini is a perfect fit in length, comes out exactly where the one on the plans does, but the Saito is nearly 3/4" too long.
Back to the stash. Grabbed the YS 63, perfect fit, and 1 ounce lighter, but how does it compare power wise to the 100? Guess I need to find a prop for it and see how it runs now for sure. Do I mount it inverted, or sideways? All these need to be answered before I pop out the T-nuts and plug the holes for the OS.