Only my viewpoint and I stress that T: ;
The reimo multirail fits on the van roughly where my cheapo one is.
I'm certain my motordome tourer wouldn't fit well if the rail were higher / further in ( I really can't speak for other awnings).
Properly painted I'm happy with my simple "c" section rail where it is.
Mine is simply fixed on with sikaflex using their primer. As yet it has no other fixings and has been on over a year now with no problem. (my intention has always been to use one self tapper at either end).
I have used it with both my tarp and my awning and in really stormy weather too.
I may not be right, but that's how mine is.