YS91 Hover
I have a YS91AC in a U CAN DO, It is approx 7.5lbs., It will hover fine with a APC 16*4w turning about 10,000 rpm's, or a APC15*6. It pulls out of a hover pretty well, not a rocket but nice. I would say 8lbs max for ok 3D work and 7 to 7.5 for good 3D.