I have a solution for you, but the Ultra-Fab 2" Motor Home Trailer Hitch Receiver part # UF35-946401 will only fit bumpers up to 4" x 4" .
For your 4-1/4" x 4" bumper, I recommend the Buyers Products RV Bumper Receiver Hitch item # 337RVA24. The u-bolts will actually fit bumpers up to 4-1/2" wide so your 4-1/4" wide bumper won't be an issue. The fit will be tight enough that you would not have any play.
It's perfect for a bike rack, cargo carrier, or any other cargo accessory. Keep... view full answer...