For my 2-1/2 gal. tank, the landings for the strap occur in the exact line of the the lower hole in the tank-bumper holder below the horizontal member. Therefore, the strap passes through that hole. I don't know if that is normal, but it worked for me. I fabricated the stap from leftover tubing I used to make front fender stays. Having the round tubing through the round hole in the bumper holder improved the clearance between the two and looks like an intended fit. I don't have a picture right now, but I can take one tonight.
Markus, is your strap isolated by rubber grommeting? I think the idea of the rubber isolator in the center hole must be to reduce the amount of small-excursion vibration that is transferred to the tank, which could stress the seams. Though, you've probabaly put thousands of miles on your bike(s) without such problem.
Richard L.
P.S. If you were quick, you caught me leaving the "p" off of "passes" in the second sentence. One of those typos that could go down in lore.