Hi Grant,
I too am an archer and have been bow fishing plenty of times for stingray's. We went down to Nudgee beach with some recurves (wasn't taking compound in salt water) and they are super easy to find. You don't need that whole line/reel kit to shoot stingrays. Once hit, they will run but they got a great big bloody flag sticking out of them, so just keep plugg'n away until they stop. I've got some photo's somewhere with about 8 arrows in one ray. lol (Kinda cruel i know) Make sure you got some nice broadheads though. (Cheap ebay specials as you're not shooting for distance and they don't need to be perfectly balanced, plus they'll rust up in a day or two. lol)
As for legalities of it, as far as I know, it's legal to shoot them, as long as you are as humane as possible. Also, if you don't intend to take them for eating, cut the tail off (once they're dead) and take it up to a rubbish bin. Then you can just leave the dead ray in the shallow waters and will be washed out next tide.
Where I went was Nudgee Beach, the entrance to Nudgee creek which is between The main nudgee beach and shorncliffe. It's a shallow creek and opens onto sand flats so a prime spot for rays.