I got a queen size memory foam mattress top at target for about $12 a couple months ago. It is about 2" thick, think it would be perfect folded in half or in thirds for a bench seat.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth