I hope any alert and better-informed readers will correct any errors of fact
which may follow, but here's my non-anally-informed input...

Does anyone know the history of glider cloud flying in the USA? Was it
ever allowed under FAR?

A comment regarding the trailing question above...the FARs/CFRs don't
prescribe what is possible, rather what is impossible (by regulation). If it
ain't forbidden, it's legal...even if perhaps not the wisest of acts.

Yes, cloud flying was legal at one time for gliders in the U.S. My
casually-educated guess is it became - for all practical purposes - illegal
after the 1955 mid-air between a DC-7 and a Constellation over the Grand
Canyon, after which the guts of today's ATC became the regulation of the
land...assigned IFR cruising altitudes, continuous radar contact, etc.

Johnny Robinson was probably the first U.S. glider pilot to become proficient
on instruments inside convective clouds, and at one time it wasn't rare to
(legally) go after diamond altitude climbs inside towering cu. Robinson once
essentially doubled the score of the pilot in 2nd place in a Wichita Falls
(working from memory) contest during a moist spell; as the only
instrument-capable pilot in that contest, he told me he spent the bulk of the
contest running out the side of one cu into the next, several thousands of
feet above cloud base.
- - - - - -

Was the prohibition part of the negotiation that allowed the XPNDR
exemption for gliders?

Transponders came along later.
- - - - - -

If it were allowed, would it play out any differently in the USA than it
has in the UK?

Now THERE's an open-ended question...!
- - - - - -

Did Lucky Chucker has an AH over Reno? Was he current with IFR? Did he
practice IFR in his glider?

Indeed inquiring minds would like to know. As (so it's my belief) an ex Thud
driver, I'd expect him to have been quite instrument proficient once upon a
time, but the devil is in the details...
- - - - - -

Bob W.