Hi 435 Thanks for the thoughts for sure. When you say rails are you meaning the frame rails? As far as loading I agree totally, but in this case I will be using a cool lift that I used to use for my truck The Neo-Dyne AU200 system Works with a cordless drill and you don't have to push bike up a ramp at all.
Ken, by rail, I'm referring to the steel channel where your motorcycle wheels are sitting. Any movement of the carrier will be magnified by the extra distance/height from the RV's rear axle.
The carrier used by Rustynuts seems to address my concerns about extra movements with some bracing.