Is My ARE Z Series Cap on Completely?

I had my cap painted about a month ago. The shop owner put down some new double sided tape and placed the cap on my truck (the thick stuff). I tightened it down. I've noticed water in the back of my truck near the hatch, and on the left front wheel well (the slot for 2x6's). But I can't seem to find any trail of where this water is coming from.

So now I'm wondering if my shell just needs slid forward a tad. I took a photo to measure the distance between the rear door and the front of the shell. Looks like it's almost exactly 5 inches.

I'm wondering if anyone else with a 2nd gen Tacoma and ARE Z-series can take some measurements and let me know what this gap should be. Usually the cap just kinda slides into place.

 

What does it look like at the rear? That gap is pretty much what mine is.

 

The back had about 1/2-inch gap. I ended up removing the front bed rail inside the bed. That allowed me to move the cap forward a 1/2-inch.