wshall,
I also have a os 91 fs. I am using a Graupner 14-7 prop per Minnflyer's recomendation. I have 5 flights on my skybolt now and i am starting to get her setup for my style. (i would have alot more stick time on this beauty if the weather wasnt so terible here in michigan) Moving the balance back to 5" by installing a pilot. (flew too nose heavy for my taste) Mine is built exactly per instructions and the graupner 14-7/os 91 fs pulls it very well. It turns 8400 rpm at a rich setting, (1st 2 tanks) You will have to pull the power back so the vertical uplines dont get to high on yah with this setup. (i lose sight of it otherwise) I wouldnt call it "truely unlimited vetical" but very close.

as for the covering i agree with darock about the "stubborn as a 4 year old" wrinkles. My wings were great, my fuse was ok, i should have used a heat gun on the fuse first then went over it with a iron. I think if a heat gun is used carefully then you have exellent results. Its not that the covering job is bad its just that there is so much trim layered on. If you used a iron first then is kinda shriks, kinda irons on some wrinkles because the covering adheres to the wood before it can shrink a lot. (this is what hapened with my fuse however now it looks great.) after 2 trips to the field and 5 flights the covering looks good as new.