I was still using the 91 on the second film. I just got back from flying today with a Saito 100 and man what a difference. On the 91 it was swinging my 16x4W at 8600 but with the 100 it was up to 9800~9900. The pull out from a hover is like a 2 to 1 power to weight ratio. I also used the same right thrust configuration and still flew straight vertically. In my opinion, the Saito 100 is the perfect engine for this plane.