MX4 install - rails

So, I noticed there’s a decent amount of water leaking into the MX4 I picked up off of FB marketplace a few weeks back. I know the shop it was purchased at, and even picked it up there after they uninstalled it from the guy I bought it from.

Question: when I put on the rails do I push them up over the raised areas on the bed caps? Or push them up against them so they’re more flush with the bed caps vs on top of the raised areas? Wondering if, since mine are slightly over the raised areas, water is seeping in the gap.

 

I installed an MX4 about two weeks ago. My rails are just to that ridge but not up and over. No noticeable water intrusion on my end.