After two seasons the foam outfitting that had been moved from my S6 to a loaned 7o and then finally to my new 7o was getting a bit tatty and lose. I had purchased last year a plastic C1 seat that I had fitted to an old InaZone. This seat had to be glued in. I did not want to glue the seat into my 7o so I went about carving a new rear bulkhead that extends in to the cockpit to hold the rear of the plastic seat in place and form the back rest. The front bulkhead was fine for holding down the front of the plastic seat. Hope the following photos show clearly how this was done.

To stop the back of the seat from moving I have inserted a rod from the seat back in to the back bulkhead

Note the hip pads are just thin strips of foam ducked taped to the cockpit rim. The straps are snowboard bindings bolted to the K1 seat fittings under the cockpit rim and the ladders attached by some looped cord to the snap shackle, which is the quick release device. The snap shackle is tied to the seat. I would not advice using snap shackles as quick release devices as they do not release the cord freely. I would recommend a BA harness quick release buckle.

Below Pics of the strap system in my Spanish Fly

Below is the old foam outfitting being taken out of a S6 and installed into a 7o.

The following pictures are of Ken Hughes Jackson Allstar C1 conversion