Nothing is per-say wrong with rubber banding it in my opinion. Myself..I just wanted the security of the ziptie. One tie, no fishing to get the band place. No dried up bands. It definately won't go anywhere until I snip the tie. Then to reinstall is a simple matter of working one tie under and up around the tank. I didn't have any ties long enough, so I do what I've done several times and just zip 2 together to make one longer one.
You don't have to change a thing in the plane, just one zip down and around the tank floor. Works from the port on the top front, right above/behind the firewall.
I guess I didn't like the idea of trying to reach the rear posts on the tank floor. Has anyone been able to do this? Reach the rear band-post.? With a wire fashioned correctly I'm sure it could be done, and I contemplated that.
One zip-tie fixed for good though. Also I'm running a 12oz. tank. The only diff in this though is length. Which makes no diff in mounting system. My 2cents.

PS I'm glad it worked for you Saso, and you haven't had any problems with bands breaking? I've got bands that seem to just dry up and go away. Maybe I need some new ones. For now though, zips seem to work everywhere an band does.