It's really awkward to fly in a Centrair Pegasus single seat glider with more than one person on board! Nice thing about a long cross country in a single seater, you don't have to apologise for farting in the glider.....
Seriously, in that same pegasus, tail number 987, I did all three diamond awards in the UK. The 300 k predeclared triangle, the 500 k distance, and the gain of height, over Deeside gliding club in Scotland, to 20,300 feet. Attested by two separate recording barographs and the tug pilot! and the BGA. And the FAI. And in the case of the distance flying, by the club holding the registered competition. At Husbands Bosworth, they saw that day coming and we all got an early start; 50 gliders took part, 27 got round the 511 kilometer task, and I was the slowest. But I got round! Me and 987!