Hi All,
I have an unused heavy steel pan which looks similar to Don's picture.
It will sit on my rearcowl but I have never considered using it as the upstand around its edges looks lethal.
My "original" seat has a rounded steel pan but as it had rust, as well as hard foam and cover, I managed to find a glassfibre based seat, possibly from Conway's in Chas Guy's day. This had a soft foam and cover and after very few miles was excruciating, feeling as if I was sitting astride a fence top. I think the soft cover was riding up and bunching in the middle. The glassfibre based seat was made before Phil set up WCS, so I can't blame him. I replaced the seat with a home made one comprising a flat fibreglass base (skilfully cut from the side of a solidly made water tank) fitted with the foam and cover from a proprietary "king and queen" seat. These were sold for use on unit Triumphs and Kawasakis. See avatar. The base is cut out to miss the oil cap and wheel arch and simply bridges the tool tray. The standard hinge is bolted to a 10swg aluminium angle plate fitted to the front of the base. The foam, which is longer that cutout in the rear cowl, is relieved to sit over the wheel arch and the top cap of the cowl and nothing else locates it. It hinges up and folds down straight without the need for a catch. I find that my specially developed posterior prevent it from lifting or moving once I am sitting. The cover was extended to allow it to tuck under the base and to isolate the glassfibre & foam from the paint. It has Velcro stitched all around to grip the other side of the Velcro stuck to the base. The vinyl seems to have protected the paint adequately for some years and several miles.
As I was not the Knight's first owner I cannot state for sure that the round based seat was factory fitted but it seems more than likely. None of it seemed fit to reuse, except possibly for patterns, so I have never dismantled it. The steel has rusted but appears to have been a much lighter gauge than the folded base.
Cheers,