I'm think of mounting the strap with a bolt directly to the lower control arm and using a 4in long 1/2in eye bolt, puting the strap through the eye part and the being able to adjust it by moving two nuts.
My only concern is the angular load on the eye bolt would break it. Plus the part where the upper mount is doesn't seem very thick, so even of the eye bolt were not to break, it could bend and angle the frame downwards. I'd make it so the eye bolt is is threaded as close to the "eye" , (so the strap doesn't have much leverage) and use large washers on both sides of the mount to add support.
But putting it into perspective I now see a whole lot of forced could be punched out going over a bump. I just like the idea of it being adjustable if the strap does stretch or what ever
It kinda coming down to just bolting the strap directly and accounting for maybe an inch of stretch? (12in strap)
Guess we'll find out here shortly