Pace stated that
Already aircraft capable of IFR flight (Gliders are NOT) ...
I must be missing something here. Why are gliders incapable of IFR flight? The relevant rule seems to me to be:
...an aircraft in level flight above 3,000 feet above mean sea level or above the appropriate transition altitude, whichever is the higher, shall be flown at a level appropriate to its magnetic track,...
Since gliders don't do level flight and are either climbing or descending they are in exactly the same situation as other traffic that is climbing or descending. Entirely legitimate.