Watch the YouTube video in the Peggit description. He recommends using a bolt instead of the push part of the rivet. Mostly for convenience but it should also make it stronger, at least wrt vertical shear strength.

I think the rivets would be quite strong, especially when using bolts. I'd expect the board to give first, but it requires some testing. I do tend to agree that a fully printable option would still be better though. A fully printable Peggit compatible solution should be possible.

For mounting to pegboard, I've done a bit with Sy's Peglock system, which uses a hook and mount - www.printables.com/model/249871...

There's also Peggit, similar idea but uses automotive rivets. I haven't tried it yet but it looks promising - www.printables.com/model/997837...