Ken - I'm working this exact issue on my 390-BH right now.
Ground to centerline hitch = 16 1/2 " (aired up)
Ground to TV connecting pins = 24 1/2 "
Solution = 8" riser
Biggest question I have is how long must the shaft of the riser be to clear the tail of the MH.
Receiver on MH length = 8"
Length of MH overhang = 6"
Shaft length must be 15" (min) to clear the tail end
Working to verify all this today and will post answers.
With my Roadmaster Sterling All Terrain tow bar, I have a +/- 3" to work with to stay within operating limitations.
2014 Berkshire 390BH-60
2007 Explorer Sport Trac