I know a report of one Sparrowhawk that showed up at a commercial operation
for a tow and was denied. He could not produce an airworthy cert that said
it was a glider,

No where on the Experimental airworthness certificate or on the registration
does it say the aircraft is a glider or airplane or anything else. There is no
box on the Application For Airworthness form to check for glider or airplane.

I just got finished having an Experimental, Exhibition airworthness certificate
issued for the first Pipistrel Virus to be licenced in the USA. N937R. Both
the DAR and I were puzzled by this but is it standard procedure.

You can licence almost anything in the Experimental catogory. It need no have
certification for any other country or if it does the USA may not accept it but
you can still get an Experimental Airworthness certificate issued for it.

Robert Mudd