Stevie334, I think you would be happy with either the FS70 or the FS91 on this plane. The 70 will fly it very well and will give good power for about 80% of the stuff the plane is capable of but the 91 will give you power for 100% of the planes capabilities. I flew my first UCD with a Saito 65 and it was by far my favorite plane to fly and relax with, my second UCD has a Saito 100 on it and it's taking a little time to get use to it but both engines sizes have been very fun on this plane.

As for the FL70[:'(][:'(] you might as well just send me the money and let your plane sit in the hanger because that's what your going to be doing anyway if you put that motor on it. One of our club members bought one due to the low price and hasn't said anything good about it in the 2 years he's owned it.
The FL70 has an air-bleed carb so there is no low speed needle valve[&o], it has a non-ringed piston, and it has a plastic back plate.

rmenke, you really think your YS63 has the same power as a Saito 100? My 100 is turning an APC 17x4W at 9600 rpm's, I don't think a YS63 will do that.