I'd put the pin about 4" from your axis (if you really want a big backend), but since your ball speed is not quite in the cranker range (usually around 18-19 mph), I'd place the pin at least 2 1/2" above your midline, in order to insure some length. Depending on how much actual oil there is, AND what your tilt and rotation are, I'd place the CG no further than 4" from your axis, maybe closer, like 2.5-3".