I switched to the Paco de Lucia form many years ago, for classical, flamenco and jazz playing, and found it very comfortable and "natural", compared with the footstool. After I developed focal dystonia (not caused by the position), I struggled for years until I found Jerald Harscher, who encouraged me to find my own comfortable position to retrain my brain and hand. I eventually returned to the footstool for most practicing, as well as standing with a strap and occasionally, mostly on jazzy gigs, sitting in the Paco position. I have suffered zero physical problems with any of these positions, so there is certainly a great deal of luck and a bit of self-awareness involved in positioning yourself to play such a difficult and unwieldy instrument. Of course, playing any instrument is difficult and unwieldy, and, interestingly enough, as many as 80% of conservatory students play with pain.
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