Good job on the 91 gene-Totally worth it. Probably the only engine i would buy at a swap meet (price being right of coarse). They just run perfect. I did a build on a 4*60 i think you read it, the 91 in that thing has been outstanding from day one and 80+ flights later. Bought another one before Tower or OS jumped the price. I think it came to 215 or 220. Feels like a great deal now. Good luck with it.