Fuel Tank Sliding???

I'm looking for advise on how to keep my fuel tank from sliding back off the front frame mounts when I ride.
And Yes the washers and rubber grouments are all intact. My seat is further back then most and is not holding the tank. rear tank strap is good also. Thanks in advance for any suggestions. John

My tank can slide some, too. It has a rubber strap to hold the rear of the tank down, but the strap allows for lots of movement. My seat is the only thing stopping it, and so the seat rubs on the tank. I put a pad between the seat and tank to keep the paint from rubbing off.
I was thinking of replacing that whimpy rubber strap with something that wouldn't stretch. Maybe a nylon strap with velcro so it will cinch up tight?

I was thinking of mabye a bunge cord shortned and mounted up in the middle frame cross bar, it already has a threaded nut welded a little off center.