Just FYI: I ordered my Seat Concepts seat with the extra-firm foam because I am a large hairy galoot (see photo above), yet I have a bony ass.
It's perfect for me, but my wife is NOT AT ALL happy with the hard foam on the passenger section. As is common amongst the fairer gender, she weighs a lot less than her gorilla-like mate yet has a, um, er, better sculpted tail section. (I'm trying to be delicate here, dammit.)
I asked Seat Concepts if maybe they could sell me a softer passenger section. Perhaps if a rider section got messed up in production, they could saw off the back and send it my way...?
They essentially passed out laughing, but I still think dual foam would be a very good idea.
If you're getting a Seat Concepts kit and you want your passenger to be happy, you might want to lean toward the softer foam if you're not sure.
2002 Suzuki DL1000 V-Strom, Dark Metallic Space Blue
1983 Suzuki GS850G, Cosmic Blue
2005 KLR685, Aztec Red - Turd II.2, the ReReTurdening