Flip top fuel door problems

So I bought a delrin adapter from a member here to adapt a flip top door to my Swinger. No problems with the adapter, but the damn door does not want to stay closed, not even when its off the car, it just keeps popping open. it seems that the edge on the door part that is supposed to catch on the release button is just so small. The cap itself is beautiful and looks great though.
Has anyone else run into this? I seem to recall a thread about it here, but I cant find it anymore.
Ive emailed the company I bought it from, but I doubt I will get any satisfaction, and will just end up with a real expensive paperweight :mad: