A properly installed Lexan lip will not come out.
First slip the lip in place without glue and get it lined up the way you're going to want it installed.
Next scribe a line around the area where the body of the bait touches the lip. In other words, scratch a line with a knife blade or a nail head around that area where the glue will be inside the lip slot.
Then remove the lip and scratch up the area of the lip that will be inside the lip slot (your scribed line will be your guide). A rotary tool with a sanding drum works nicely, but a carefully applied file blade could do the same job. Just rough up the lip so the Devcon has something to stick to.
Finally apply Devcon 2 ton epoxy to the lip with the area you roughed up on the lip and inside the lip slot. I use a popsicle stick for this.
I also like to drill a couple of holes in the lip within that portion of the lip that will be inside the bait. The holes allow some of the Devcon 2 ton epoxy to form sort of a "post" within the lip slot for extra added strength.
Slip the lip in and carefully wipe off any dripping excess glue.
Lastly, I like to hit the perimeter of the lip slot with a heat gun to remove any bubbles from what little exposed glue remains.