I load Mag-Tech 16ga brass shells also, but havn't experienced the troubles that you mention. For glue on the overshot card I use a GE silicon adhesive and the OS card stays in place. Of course I don't experience the temperature ranges that you do, and that may be why I've had no problem with the glue holding.

I'm a little confused about what you are calling a base wad. The cushion wad on top of the over powder card?