5'11" here too and happy on a large SB130. Never tried the M but I suspect it would feel too cramped. FWIW, I rented a large SB6 a few years ago and it felt too big for me....Wondering about real experience riding a medium at 5’11”. Coming off a large SB6 that at times felt too big but not always.
This size comparison chart is sick, thanks for the link. And thanks to all that have shared their experience, it has been helpful.Go large, hopefully this works