Decided to go with the carriage bolts and T- nuts.
I started bench work this week. I am re-using lumber from my last layout as much as possible. 2x6 frame. 2x3 legs. Nearly got the right wing done. I need some internal cross braces. I think I'll be using 1x4 for that.
Once that is done, I'm going to move the workbench away from the wall more and find a piece of plywood for the top of it.
Then, I'll work on the left wing. That one needs less math since it will just be a trapezoid where the three walls and the workbench are the sides with a diagonal to close it up.
Then comes laying track!