OK, got a little more use out of the pre press and it def makes things quicker, simpler, and much less fuss. I wish I'd had one right from the start. Highly recommended bit of kit, IMHO. Loading up the bags is so much less fuss and hassle and pressing itself is more straightforward. I havent yet, but Im pretty sure I could do two ounces at a time now and not lose any yield. Its much easier to press 20g now I have a pre press, I can tell you that much
Speaking of which, pre - press plus the 15 u bags is fantastic. No loss of yield at all and the rosin is fucking lovely. I've resolved my over packing and over pressing issues, and if anything, yield has gone up ever so slightly.
15u bags survived completely intact after a first press, fold, and then going in for a second press. Not a sign of any slight split or breakage on the bag.