Could you use a piece of ply like a stretcher? strap hand truck to the 28" x 6 ft. board. Add some protection on the bottom like carpet. A few cutouts in the wood as lifting handles. Lift and slide along the back cross rail of the rack? Strap as usual. maybe some cross pieces on the bottom of the stretcher that are spaced to drop just in between the front and back cross rails to prevent sliding forward or back. Then ratchet the whole thing down.
Just an idea. I think you'd have to test. would make getting down easier too.