A friend has a Saito 100 in his UCD 60 size with an APC 16-4W and it turns right at 10K RPM on 15% fuel. The weight difference isn't an issue. According to Tower and Horizon's website's, the 100 is actually lighter than the OS FS70 S2.

I also have a NIB UCD 46 and am trying to figure out what engine to power it with. My choices are: Saito FA 100, FA 72, or an OS FS 70 S2, or a Magnum XL-70RFS.

Most of the UCD 46's i've seen are coming out tail heavy so I am going to wait untill the airframe is complete to see what it'll need as far as balance.