I agree with AC If one Jacks a fifth wheel back to 90 (and the under carriage is still in tact) what good does it do? The turning radius of the pick up is such that you can never go any farther back because you could not turn the pick up sharp enough to keep up with the 90 degree jack, at least all my pick ups have been that way.
A 90 degree jack back was possible when i drove an 18 wheeler with cab over tractor, but the short turning radius of the tractor was there to do that and also the suspension on the trailer could withstand sliding the wheels sideways.
