may be the wrong thing to do, but could it be that you can just file a bit off the end of the tube so you can screw the crown down more? OK that sounded crude, I mean you file it down, then bevel it proper, then smooth the edges with 1000, 2000, and then jewlery rogue so mating surface is mirror smooth for waterproof...
I wouldn't opt for this option though. It is obvious that the internal thread spec of the gen. crown is different to that of the rep crown too if it can screw down sitting flush against the case whereas the rep can't.
There is very little room to play around at the top of the tube actually, and by filing it down you may run into ruining the waterproof ability.