I have to use a drop hitch.. Now.. Out side of the BLue Ox Factory or some place like it finding a welder who will modify such a device is... Not easy.. But I had a 2nd (And 3rd in fact) receiver welded on the drop hitch.. One for the bikes, one for the cargo tray, and the original for the car.
Replaced that one (Still have it in basement I think) with a shorter drop.. This one Blue Ox customized for me. with a 'Tong" for a ball hitch,,that's where the bicicle carrier mounts.
But you can get factory double adapters. Some are "Straight through" Plus either drop or rise (Often 4") the others are liek 2" up and 2' down.
Most bigger RV places will have an assortment.. You might get lucky at an auto parts store or department
And U-Haul hitch world. if they don't have it in stock. they WILL order most anything.
And last.. I recommend an anti-rattle device (Quiet hitch, Blue ox clip. these devices lock the hitch adapter so it does not "Rattle" (move) in the receiver.. If you are going to haul bikes you need at least one possibly 2 or 3 of these clips.