I'm running an OS .70 FS in my laser, and based on the horsepower you guy's posted for the YS .45, I think that the 45 will be a great choice. How much does the 45 weigh?

Ounces in this plane mean a lot, so if you can save a half a pound with the same (or more) power, that's what I would do.

The worst that can happen is that you will have a blast with the plane, and maybe want for a little more power at times.

I say build it, put in the 45 and fly the hell out of it!!!