I think one of the important areas for adding to this design is the actual weight of the roller.
I get the feeling that the original one is quite solid, much, much more solid than a PVC tube, which would make sense that the idea of this is to reverse the shape of the paper fibers causing the curl. Of course you can press on it when you roll but I reckon a heavier core may do an even better job.
I suggest filling the tube with sand or something even heavier, (small ball bearings?) and sealing the ends.