I wouldn't say centered, because of the width of the edge of the rear capping it's really closer to the front by about an inch. In my case the front of the rail is about a 1/4 inch away from the front edge of the tub, just in line with the bulge of the top tub capping.
It is pressed right up against the top capping.
I think these things were added at the dealerships and could be all different though, and I'll warn you that I have not tried a soft top with these yet. Maybe wait for someone else to confirm theirs is this way too?