Height from ground to center of receiver hitch on MH is 14.5". From ground to center of base plate on toad is 16". Do I need a 1" rise? 2" rise? or is 1.5" difference not enough to worry about? Using Blue Ox base plate towing system.
Yes, get the riser. You should strenuously avoid a situation where the toad end of the tow bar is higher than the coach end. That encourages the toad to "climb the tow bar" in a sudden stop, lifting weight off the toad front wheels and maybe even jumping over the tow bar and crashing into the coach. The tow bar should be level or slightly upward at the coach end. I'd use 2".
Is it enough to worry about? Not until the day comes when you have to slam on the brakes (and then it's too late).