thanks for the help. I think I'm keeping the rear fender, a bit of it at least. so I'm wondering how I should do this. it's going to go up in the back, not lay flat like yours, I'm thinking fiberglass is the obvious choice for the seat pan, but I need to figure out how to mount, whether to use the hinges, brackets. whether it should go over the frame rails or right on them like yours.
and whether or not I should cut the frame. might weld on a loop. but it would need to slant up for mounting the fender.
thanks for your input. also, is your seat cover removable? it might be too late, but...
I am a painter- bikes, houses, etc.. there is a product that I use for restoring wood with rot issues or preserving new wood. it is a couple epoxy type of products, one is a penetrant to kind of petrify the wood, the other a filler. both are 2 part. the penetrant soaks into wood, the wood will suck it up until it's full of it, then you let it dry. after this it is as durable as plastic. it will never rot and never absorb any moisture. I thought it would work well on your seat pan.
the filler is awesome. it can be used to fix fiberglass, wood, concrete. you could build a seat pan out of it. I actually thought about it. but it's around $200 for 2- 1/2 gal buckets(part a&b) of the filler. the penetrant is only $30, though. and it would make your seat pan last a lot longer. if you have a good paint store by your house they might carry it. mine does but the mark up is a lot.
it's called restor-it, here's a link:
http://www.restor-it.com/this place sells it, I just bought some from them for a job I'm doing:
http://shop.sailboatowners.com/google/custom.htm?vp=91164this one would prob be enough-
2-Pt Kit Restor-It Clear Penet Epxy (Mfg No. CPES-8COLD)
IN STOCK FOR IMMEDIATE SHIPMENT SO-132539 $28.34 US