I have to agree,the .60 size UCD will hover with a .91 four stroke!!I had a well used OS.91 on mine and it would hover all day long with an APC 15-4W.We now have the .46 UCD with a Saito 100.The UCD's are not my favorite planes,but the .91FS does work well on them,I would put that .91 on a .46,though.You could sell that .91,get a 1.60FX,and an AW 80" Profile Extra and be in 3D training heaven!!!Well worth the extra $$
Mike