In my recent experience Ilford 35mm films are curling a lot more than Kodak and Fuji. The base seems to be a little thinner than it used to be? I've only had the problem you mention with Ilford films but not Kodak. I use heavy weights and after going into sleeves I generally leave under a pile of heavy photo monographs overnight. I also concur that fast heat-assisted drying also compounds the problem.