I reckon you're pretty safe. I've watched a lot of videos on leatherworking, particularly holsters, and never seen one glued curved, they're always done flat. In fact this site, so far, is the only place I've seen the method discussed. I've only done one holster this way and it turned out fine, although I cut the liner a bit oversize to allow for any mis-alignment while gluing up and then trimmed to size after.