Big thank you to Tuned8e and Myke75. I took a bit from each of your methods and just got this done on my 2015 GC Altitude.
I did purchase some M6 25mm bolts for the four middle mounts on each side. Seemed to me the "bright side" rails were a little taller than the decorative rail at the mount point so I wanted the extra security the longer bolt provided.
For the front and back bolts on both sides I used the factory bolt, but I placed a 1" stainless washer under the bolt head and then placed the factory 1/2" fitted washer under the 1" washer. That factory washer held up the 1" washer while I slid the new rail into place. As with Myke75, I did have to file a little bit off the top of the front bolts for the housing to slide into place, but not much.
Also, just put on the mopar cross bars. Super easy install except for the black plastic top flap which did not come installed. It took twice as long to get these pieces in place than it did to mount the cross bars to the roof.