Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
The reason I mention it is the bike in my avatar pic (Yamaha he whispers) does the same , it even gets in down my neck, its 'orrible. I'm slowly moulding a new rear seat unit to stop it.
I used re constituted foam, 1" thick and stuck 2 together with HD spray glue. Easy to cut to shape and sculpt with an electric carving knife. After I made the vinyl cover, I stretched it over the metal base Trig made for me and pulled the cover really tight and held it in place with that silver carpet tape. We then used this metal upholstery strip but cut the spikes off and drilled through the holes in the metal strip and the metal pan and held the strips in place with pop rivetts.I'm just about to make another seat for another project bike so I will take some pics of the underneath so you can see what it looks like. (Attachment Link) (Attachment Link)
Photos for Phil (Underdog1) of how I made the seat