pox67: That's similar to what I ended up with. Although I didn't think to use the wing strut supports to anchor the rubber bands. As long as those stay put, that was a good idea. What I did was to take a couple pieces of carbon rod about 1/2" long, and stab them into the fuse on either sides of the battery area, glued in with epoxy. Then I used those as anchors for my rubber bands. I ran two sets just to be sure, one in the front, one in the back.
Here's a pic when I had three carbon tubes. As mentioned before, I've since changed to four (two sets). You can also see my custom battery door, that was necessary for my 2000mah 3S lipo to fit. It failed by the way! lol Hence the need for the rubber bands.
I think, as you mentioned, I had a problem with the epoxy not sticking to the plastic hinge lock (which I re-used) and it opened during flight.