At the risk of starting a riot and being branded as an outcast, I will mention an experiment I conducted recently by utilizing a football forearm guard as a sleeve to provide additional right arm padding and comfort while playing for extended periods.
Rather than using the guard with the padding facing outward, I turn the padding to the inside of the arm, and it is so very comfortable. The fit is firm and snug, and it does not shift or move around even after using it for a long while.
The outside of the sleeve is a tightly woven nylon, so it is quite smooth and allows easy right arm movement across the guitar without hanging up.
I realize that playing the classical guitar is not a contact sport, but it worked so well that I plan to continue to use it, even if it means I'll be mocked and jeered at from this point on!
The price was only about $10.00, and I've got two "guards" or sleeves that I can use. Just thought I'd share this for anyone else brave enough to try it!