The difficulty with closed courses in older gliders is headwind - they climb very well, but the polar drops off substantially as you speed up plus general speeds are lower than newer glass gliders, so it's easy to end up in the situation where you take a climb and get blown back during it, then glide out to the same point where you pick up another climb from the same thermal source...
However the last day of the Club Class Nationals that finished at Lasham last Sunday was a 510km task which 38 of 41 gliders completed. The day was won by a K6. Club Class is handicapped and (I think) windicapped. The alter attempts to balance out the effects of a headwind on different gliders.