I'm going through a bathroom remodel and hit a point in installing the shower door that has me nervous to continue: I put in a Dreamline Slimline 60x30 shower pan and now I'm installing a Kohler Levity shower door on top of it. I put the shower threshold down and saw that there's a gap in the center of the threshold, roughly 1/8" at the center. The two ends by the walls sit flush, but I suppose the pan edge bows in the middle (perhaps from the shimming I did).

The shower calls for just using caulk to secure the threshold. I'm nervous about caulking it and taping it down flush since that will create a constant upward pressure on the caulk, likely separating at some point. Could I just use a thick bead of caulk instead and have that take up the gap? Any other ideas?