I believe Ton Kooiman's Forza thumb rest/hook can be purchased with a plate that can be soldered to your horn after the current one is removed. They are not cheap, however, $150.00+. After removal of the original and installation of the plate, the Forza is screwed to the horn.
you can indeed modify a metal thumbrest but it will deface your horn and change its looks permanently (especially if, as I suspect, your horn is silver or nickel finish). So what is exactly that you are seeking to achieve? If it is too hard you can accessorise with a cushion.
A forum community dedicated to saxophone players and enthusiasts originally founded by Harri Rautiainen. Come join the discussion about collections, care, displays, models, styles, reviews, accessories, classifieds, and more!