RE: Vector 300, OS 90 3D?
Started out with a 91 FX with APC 13X8, now my preferred prop is APC 14X6. Out of sight vertical straight off the ground! A buddy is using a 91 four stroke and it flies great, although with less punch than the FX. Not much into 3D, but the 91 FX will hover it and do the high alpha stuff with the CG moved a bit back.