When I was younger I had a gollner 200 mono and a fantic 200 and never had a problem with my brakes, I can only put this down to regular maintainance I think the shoes that were used was ebc. This will sound like a bit of a ball ache but the day before a trial I would remove both wheels clean out the hubs and wire brush shoes reasemble and adjust up but this would give almost as good as a disks of the time.