2x10 I see no reason they couldn't be a 12 though.
I've never hunted from them. I built them to practice off of. Which would be basically the same. I've only tried them on pine trees in my lawn. Once they settle they are very solid. I tried putting two on a strap and that doesn't work.
The diagnal board is knotched. It's glued with outdoor wood glue and all screwed together. I weigh 215 without gear and I've never broken or shifted one. If you alternate the grain when putting them together and glue them it's a lot less likely to split.
To be honest I didn't put much thought into them. I needed something quick that I could leave up for practice, and for that they've been great. Way to heavy for me to do any Mobil sits but I'd say they'd work for a preset.