Rear hinge pin popping out

[colmo]

My Madrat is starting to go really well, but the aforementioned problem is driving me to distraction - the rear left hinge pin won't stay in. Starting fourth in the B final on Wednesday, I was just passing the leader inside the first lap when he tapped me on the rear left wheel and it fell apart for the 3rd time that night - despite me changing the rear brace.

It seems to be caused by the inherent flex of the T-piece (the newer toughened one Battleaxe gave me at Oople - thanks again!) and the braces, plus the braces seem to get worn very easily.

I could solve it with the alloy hingepin braces and carbon fibre T-piece, but that would cost nearly as much as a B4, which is ultimately my other solution to the problem.

Are there any other cheaper fixes I can perform?