Leather seats will for sure weigh more, I'd be surprised if it was as much as 20 lbs per seat (fronts), could be just 10 lbs more. Just a guess. My L99 is a 1SS/RS. I will try and weigh again this week.
PROJECT HEAVY CHEVY: 2010 Camaro SS/RS |1SS | L99 | CGM
13.15@106 1.95 | Stock
12.06@110 1.70 | Bolt-Ons
Mods: Rhino Tune | Kooks Headers + Cats | Circle D 3200 | New Era OTR | R Crawford Manifold | 305/45R18 NT05R | Moroso Spiral Flows | LSR Suspension | Powerbond UDP
LSX Record List: http://www.planetlsx.com/forums/showthread.php?t=5431