I'd ask JimR about the shipping bags..... I know he's been down that road.
For the stinger, I'd seriously try heatshrink. Not the cheap crap. The good stuff has glue in it. Make it an inch longer then the barb, the stuff stretches so you should just be able to stretch it with needlenose if the barb is too fat. If you grab the base of the stinger with hemos or needlenose you should be able to get it far enough away from her tail to hit the very end of the stinger where the point is with a lighter or torch just enough to get the glue going then just pinch off the end.
Another option I see being a good one would be silicone vacuum line for cars. Or even vacuum line plugs.
Styro is probobly a poor idea, I guess I tend to overlook barbs cause it seems I've had a lot more issues with the rays biting through the bags then ripping with the barb.
I've been told it's best to slightly cramp big rays when shipping under the principle that if they have room to move then they try harder to get out and can build momentum, while if there more pinned they seem to accept it and don't try as hard to get out. Not sure if there's any truth to it or not, but none of the big rays we've shipped have been lost.
Can't count how many have been saved by the pondliner trick. Almost seems they're gonna get through the bags no matter what, wit the liner at least the water stays in..... Provided the box doesn't get flipped upside down.
I don't have near the experience you do shipping but have seen some big rays shipped. Figured tossing ideas out isn't gonna do much more then lead to other ideas.
I still think someone needs to create some large airtight resealable reuseable shipping containers. IF someone doesn't make this happen soon I'm gonna get creative...... Really don't see why these don't exist yet given the price of rays and the idiotism involved with the people at the airlines that handle our fish. I bet you could get one to withstand a 4' drop upside down without breaking/leaking. Build a half dozen, put a deposit on them and just have them UPS grounded back after the ray gets to it's new destination.
We use controllers that email us when stuff goes out of range, or to control waterlevels, or temp, live internet feed of tanks but yet when it comes to shipping it's a box, some styro, a few bags, some hope, and a prayer that our rediculously expensive investment gets to its new destination in a salvagable condition...... Doesn't take a rocket surgeon to figure out this doesn't make a lot of sense..... lol