Still working on redrawing the plans and I came across an anomaly. The back and sides are solid wood panels. The side panels fit tight edge to edge. The back panels have a 3/16 gap between the panels and the posts. I could believe the gap is for wood movement, sounds reasonable, but then why not in the sides. Both the back and the sides are similar grain orientation and both will be subject to movement. I suspect the real answer is that whoever drew up the original plans either wanted tight with no gaps and got it wrong on the back or wanted a gap for wood movement and got it wrong on the sides. Whichever it was it was immediately obvious as soon as I started putting the pieces together in sketchup.
I’ll add some gap on the sides and shrink up the gap on the back. Now that I have my own model I can size it any size I want and print a new set of dimensioned plans as needed.