Recaros is due to a built in design quirk - if you pull off the inner (center tunnel side) recliner cover, you'll find that the inner pivot is supported by a thick clock-spring, NOT a positive reclining mechanism. The clock spring resists backward movement of the seatback, but does not lock it in place like the outer recliner does, so constant pressure on the backrest causes the inner side of the seat back to sag, resulting in the backrest frame ultimately becoming warped or twisted (the bigger and/or heavier the person using the seat is, the sooner it happens).
Twisting it back into it's original shape is only a temporary fix, and repeated bending can (and often does) cause the thin, stamped sheet metal seat shell to crack. I've been looking for a permanent fix for this problem for quite a while (my driver's seat has the same problem, and long drives now cause considerable back pain a day or two later) - the tenative solution below should work, but will require some welding, as well as canabalizing a second pair of seats for their recliner mechanisms and modifying the seat backs.
Here's the proposed fix (verification will have to wait until one seat has been completed - I've got the extra parts on hand, and will be tackling this project fairly soon):
The basic seat shell stampings appear to be symetrical (i.e. the passenger side and driver side seat backs are essentially interchangable) with two exceptions - there are two captive nuts welded inside the shell on the door side (they recieve the bolts for the upper part of the recliner), and there's a slotted stud on the tunnel side that the clock spring mounts to. Above the clock spring stud are the holes where a recliner mechanism would mount, but no captive nuts.
At least two modifications to the seat back shell will be needed - a) the clock spring stud will have to be removed, and captive nuts will have to be welded in at the existing holes so a second recliner mechanism can be bolted to the center tunnel side of the seat. The end result will be a seat with TWO independent recliners (the original mechanism on the outside of the driver seat, and a passenger side mechanism on the inside - adjusting the backrest angle will require both hands), but both sides will be supported by a mechanical recliner, so sagging should be permanently eliminated.
Some modification to the inner recliner mechanism will probably be required to eliminate the tilt-forward latch and allow the lever & cable on the door side to release the seat back to tilt forward - the other alternative will be to have two releases - one on each side, both of which will have to be lifted to tilt the seat forward.
Interesting read Barry. I bought two real good passenger Recaros a while back from a junkyard for next to nothing. I figured it would be easy to convert a passenger seat into a drivers' seat....wrong! I can't believe Recaro made them that way; must have been designed by the apprentice. At least the seat squab is interchangeable, but the back is something else.
Keep us posted on your fix though.