The seat was always going to be a pretty simple item, well, the padding and covering at least. So after looking for some sturdy foam that will prevent butt – fiberglass impact over bumps I stumbled upon the idea of using camping roll mat foam. Apparently, according to a guy on the internet so we cant really trust him, you want closed cell foam. I saw none of this information on camping mats so purchased the cheapest. This was then cut to size, layered together with some spray adhesive and carved to fit the uneven base of the seat pan.

Its not neat but hopefully will not be seen.
The pattern for the material was cut from newspaper, and the panels were decided upon at random as I identified other areas that needed to be covered.

Cut some vinyl to roughly these sizes, chalked the outline of the pattern onto them and commenced pinning.

Just in case proof were needed.
Wanted a bit of a pattern on the main panel but kept it simple as this is the first time trying this kind of thing. Two layers of vinyl, with three layers of cotton backing material packed between them, had the lines stitched onto them. Worked pretty well but will have to see how long it lasts.

Once everything was stitched together gave it a test fit, and its not too bad. Will need to be tensioned when it is fastened properly to the seat base.

All that really remains is reinforcing the stitches in the corners and the proper fitting. Have gone for the classic cafe racer method of poppers, already have the poppers and the rivets to fit them to the fiberglass, now to finish the sanding on that seat.
Possibly related?...