I was out of town the last week, but the week before that it was fairly warm, so I was able to varnish the roof ribs and some other wood bits. I also installed a piece of wood that supports the dome lamp above the rear seat.
I cut a piece of 3/4″ plywood to serve as the base of the rear seat, and made up a couple of wooden blocks that screw to the rear floorpan to hold it in position. The original seat base was a wooden frame made up of several pieces with tongue-and-groove joints, but the plywood is simpler, and will be undetectable once the seat base is upholstered.
Spring has arrived, and soon it will be warm enough to resume body work and painting.