I Think I Figured Out Omni SE Bottoming Out
TLDR: Lumbar pushes you forward too much, seat pan/foam density too shallow (horizontally), should size up
Weight & Height: 190 lbs (86kg) 5'9'' (175cm), decently muscular, 48cm SE
I think I figured out why everyone has different feel on the bottoming out on the SE despite having around the same measurements, and I think it's due to having different lumbar depth.
Basically, when I was feeling the foam density differences with my fist, I noticed that the back portion of the seat is fairly dense AND deep. However, the issue I noticed is that there is a sharp drop off (ledge) in the middle of the seat for both the foam and the pan.
This causes 2 issues. If your lumbar is fairly extended, your butt would not be fully seated behind the ledge / on the thick foam. If you sit up straight (90 degrees or so), you're also putting pressure directly on the ledge.
Personally, the chair is SO close to being perfectly comfortable. I do feel the bottom and causes discomfort only SOMETIMES, which is why I was feeling around the pad. My shoulders are also slightly too wide for the backrest, and my thighs hang off the front too much. EVEN THOUGH 48cm should be the perfect size for me.
I think I'll switch to the Maxis even though its technically too big. The longer seat depth, thicker foam, and wider back should fix all of my issues.