Another reply from Russell Suthern:
I made the 1st batch as an R & D experiment to test different approaches. Then we had a shield making contest. Everyone made a shield and prizes were awarded for design, functionality etc.
You certainly do need a very precise shape of shield with a quite shallow curvature for rolls, or you do get tangled up in it.
I have never shot an arrow at a rattan shield, but have fired test arrows at a few of our shields. We discovered that straight-on hits were more likely to penetrate, whereas if the shield was angled, they tended to bounce off. Occasionally however, an arrow would pierce what we considered to be a really strong shield quite deeply, so there is an element of chance. I’d never risk firing an arrow at a student holding a shield, unless it was the blunt, padded style arrows they use in battle reconstructions. (We are looking into buying a bunch of these to test.)
I believe the usual style of archery combat was to fire the first volley upwards (clout archery style) so the enemy would be forced to lift their shields up, then fire a volley straight forwards as they would be exposed.
As for long weapons against shields, usually they would have a hook on the blade (you can still see this on Kwandaos, Pu daos, bill hooks and halberds.) This hook would be used to catch the shield and pull it down, so your comrades could then get to the enemy with their own spear or whatever.
We are not too precious about our shields, they were made to be used, after all. For most of my combat gear/weapons I have one good example for display, which never gets used, only admired, then another old beat up (but still much loved!) example, which gets to do all the hard work!