Technical Single longitudinal roof rail to attach an awning ?

[Minniesmum]

Have read through many of the threads on here regards roof rails and a few about front to back rails . Ive just had a pop-up roof installed to my Doblo to use it for camping-its fab. The plastic roof rail studs are still useable so great. Down one side of the car Id like to fix a single rail to which I could attach a drive away awning for my camping trips. Sounds simple enough.
The rail I can cobble together myself. My question is about the fixing points. Ive not tried to remove the plastic studs yet to see what lies beneath. Is it just a threaded hole ? If so in theory I should be able to get the right thread sized bolt maybe with an eyelet on top and just string a rope along to attach the awning to.

Any ideas, comments, suggestions welcome please ! I do love doing stuff like this myself..

 

[sludgeguts]

Yes, it is just a threaded hole (OK, a hole in the roof with a nut welded to the underside.).
I would suggest using a bit of plumbers PTFE or similar just to make extra sure no water can seep in, it also acts as a locking mechanism for the bolt to prevent it accidentally working loose.