RE: OS 70 in a clipped wing cub
I had a 70 Surpass in a 40-size CG Cub clipped,,it was a great combo,, a 91 is almost too much
It really depends on you,
if you want to fly scale like aerobatics a 70 is plenty with power to spare,,
if you want to do 3-D and hang it on the prop all day,, you'd need a 91
have fun