[Arran]

One potential problem that I could see from using hardware cloth is that if the cloth absorbs some moisture, that moisture could react with the zinc or aluminum plating and cause stains in the cloth, that and the nail/upholstery tack heads, of course you could prevent that by painting the hardware cloth or by putting a layer of open weave fabric underneath the grille cloth. One alternative to add some strength may be to use that old style bronze insect screen, the bronze is a little more resistant to oxidizing then zinc. I usually just install the cloth the same way the manufacturer did, we don't have any little ones running around poking things around here anyhow.
Regards
Arran