Funny, everybody has problems with the supports, because they are difficult to adjust for different chairs. This is why a strap is really more efficient in so many ways. The angle stays the same, even when you're standing, or sitting on a stool or a chair. It gives you the opportunity to practice standing up, moving around, generally better for your overall health. And plastic hooks can be attached using double-sided foam tape or an adhesive putty, so no drilling is necessary. I do many non-classical gigs with a Godin Multiac nylon-strung 7-string guitar, and I occasionally use a guitar synth or a looper, so standing really allows me to operate the pedals easily (not a concern for pure classical players who prefer to sit). In any event, most therapists dealing with focal dystonia or physical issues think the strap is a good answer to maintaining your overall back and joint health, even if only used for practicing.
Lester Devoe Flamenco Negra
Lester Devoe Flamenco Blanca
Aparicio Flamenco Blanca with RMC pickup
Bartolex 7-string with RMC pickup
Giannini 7-string with Shadow pickup
Sal Pace 7-string archtop