lord vulcan...it is in retrospect that i say i did not like the os91 combo on my ucd...it did tricks ok...pulled out of a hover(what hovering i could do back then) somewhat...and to be honest, i could not really do anything more than very short knife edge's (coupled all to be damned) snaps, harriers, and very shoprt hovering...

but now that i have become a LOT more 3D oriented, du eto foamy electrics with 3:1 brushless set-ups, i can say that for me, the ys will be a lot better...i know that i will be trying stoopid things like tail touches, rolling circles a few feet off the deck, crazy snaps and violent manuvers and things like this, and as best i can do them, you have to have an overabundance of "ooommph" to do them easily...if i can get 2:1 or even 2.5:1 with the ys 120 and 30% heli, then i will be happy...the plane may not survive even as long as my first one did, but at least i will have enough horse-pressure...

try an apc 15x4w on 30% and you will do ok...i am very close to sea level and that combo worked really well...i also liked a zinger 14x6 but it exploded due to an attempted harrier landing that kind of ripped the landing gear out....

good luck..

if i were you, i would try to get a bigger motor..a saito 100 is also a viable motor..from what i have seen, they have a good deal more power than the os91 and weigh a little less...but find you a 120 or a 1.10fz if you can..i think you will be happier with it in the long run..!