I just wanted to post my observations. Keep in mind that this was only one night in a backyard, so these aren't long term, repeated results.
Last night temps dropped to 0*F with windchill at -20*F, so I thought, "hey, why not sleep outside?"
I used my EE Rev X 20*F quilt, which has 30% overfill. I slept in an HMG Echo I tarp with inner, on top of a Neoair XTherm and used a Cocoon aircore pillow.
All clothing worn were Items I normally take with me on winter outings.
On my lower self I wore VBL socks, Darn Tough wool socks, Powerstretch tights, nylon hiking pants and Columbia insulated pants (kinda like lightweight ski pants.)
On my top I wore a Smartwool mid weight base layer, Patagonia R1 zip, puffy jacket, light fleece balaclava, a down hood, and fleece gloves.
All night, whether sleeping on my back or side, I was comfortably warm, even my feet. With the right clothing system, it appears I can take this quilt to temps much lower than the rating. Not bad for 24 ounces! Hopefully this will help people considering purchasing or using one of Tim's quilts. It's been a fantastic piece of gear.