That is really a nice "chair". I could see myself in it! LOL
I finished sealing the Homasote roadbed today. The platform is 1/2 plywood on L girder construction with 1/2" Homasote roadbed. The Homasote was relatively easy to cut with a 45 degree bevel using the table saw (outside of course) and then cutting kerf slots at about 1/2" intervals for the curved sections. I used half width strips for the curved sections. The saw blade was about 1/16" wide and the curve fits very snug on the O31 tubular track. It is very fragile though and I did break some pieces. The Homasote was glued down with Elmer's School Glue and held down while the glue was drying with drywall screws. (later removed) I used Zinsser Kilz all purpose water based primer. It is fast drying and has good gap filling ability.