I’m finally back from my course, and sufficiently recovered from jet lag that I have some energy left over at the end of the day to do a little bit of modelling. So, I tackled the curb around the top of the turntable pit. I think most turntables must have these, otherwise ballast and stuff will fall into the pit.
For my curb, I used an 8″x8″ strip of styrene. I bent it into a pot of boiling water to get it to agree to a curve near the pit radius, then coaxed it into position a little at a time as I glued it in place. Putty fills the gap between the styrene and MDF. Time and primer will tell whether this is smooth enough.