I remember in the late '60's at Elsinore California a glider that was
flown from the prone position, I think it was a Marske wing?? anyway
it was small and the pilot flew from his belly with rudders at the
back and head first in the canopy at the front.

I think if you look deep enough you
might find that the "head first" position
is prohibited by the FAA regs. Mac

I don't believe that's correct. I've been through the regs in 14 CFR
part 23, and also the European JAR-22, a few times and seen nothing
there that would bar prone flying. It seems to me that it's just not
the sort of thing that the FAA tends to make rules about. Besides
that, I can only imagine the language that it'd take to define a thing
like that to the necessary degree of detail.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com