Visors with the varilux have been hard for me as well--i got a magnifying lamp that needleworkers use--the "newer models" in plastic do not have the same power so I would look at a craft shop to see if they have one--other than that get an adjustable chair and play with moving ONE PIECE AT A TIME--chair, then vise, then lamp.

No Quick fix just some thoughts from times past

PS when you find the sweet spot--lock it in!!!