Have you considered alternate methods of support (ErgoPlay, Gitano, Dynarette, Murata, others)? They allow you to play with both feet on the ground, keeping your back straighter. Or you could combine a guitar support with a footrest. If using a footrest alone, make sure that you have a chair that allows your thighs to remain parallel to the ground, and you may find that the footrest is enough.
"(P)Lay on, MacDuff, And damn'd be him that first cries, 'Hold, enough!'"