Of the 5 or so nice threads on the internet and 5 million useless "search first noob" posts I felt as though I could contribute to knowledge base on this subject with pictures.
I am tall and thin (6', 170#) so much of what is already written didn't seem to apply to me.
Here is a rough image; I took out pretty much all the foam from the seat bottom. I left approx 0.5" of the stock seat foam to retain the shape. I then purchased a high density foam "garden kneeler," which was trimmed to fit in the gap of removed foam.
All foam was removed from the seat bottom bottom. This gives me approx 1.5" total padding between the metal seat base and the seat cover.
The left bottom seat bolster was rotted away so I glued (transplanted) some foam I cut from the bottom.
For the seat back (lumbar area) I removed the entire foam insert. Conflicting reports say you should have something in there; realistically I don't think you need anything if you share my body size. With the stock seat I arrived beat up for any long duration trip, this can't be any worse (Have driven for about an hour arriving with no extra aches than normal).
"While I was in there's" struck and I attempted to dye the seat cover with rit dye. I should have researched first as the fabric is something synthetic and won't absorb that dye. I painted the seats with duplicolor fabric dye in the past but it fades too. I also (poorly) sewed on reinforcement patches where the fabric was getting thin.
Overall impression; I gained 2-3 inches of head room. Nothing major but a start. The high density foam is needed, I wouldn't go with any less padding which means for more clearance I would need to change seat/seat mount. Also, my unprofessional hack makes this seat look beat. Sitting lower in the car makes it more enjoyable, a few more inches would be nice...
enjoy
