I'm a couple months late responding - sorry. This could be helpful to other DIYers
I'm in the process of installing toppers on our HC. I thought there were awning rails on ours but they ended up being drip rails above each slide. Dometic supplies awning rails, cut to length with each slide topper. They are installed quite easily** with the self drilling screws, Just be sure to inventory each box of parts that comes with each topper - I ended up short 3 bags of screws.
** Easily means standing on a ladder for several hours, first checking proper alignment with the slide as well as where the rail goes height wise.
Then an initial center screw install, next the rail is taken down for some silicone caullk at each hole, then going back up the ladder and refastening that one screw. You then go to one end and ad the rest of the screws to the middle, After that, you start at the other end and do the same thing. Once the rail is up, you go back and clean up that silicone you slobbered on the side wall.
For our four toppers, I installed 110 self tapping screws over a period of about 5 hours. I then installed the 4 sets of topper brackets which are anothe 40 screws that need predrilled holes. Not difficult but time consuming.
Traveling with my DW Susan, a couple poodlepups and our 2014 Montana High Country 343RL, being towed by a 6.7 2011 F250 CCLB using a B&W hitch and OEM puck system