Hmm, difficult question Mick as there are three of these on the go at the same time and things are a bit start-stop-start around here at the moment with the house rebuilding still in full flow, so I'm building them in odd moments when I can disappear to the workshop without being missed.
Getting my head around David's ideas took a little while, and his instructions are very comprehensive but as I came to repeat the second and third time I reckon I halved and then halved the time taken again. I had three wagons to this stage after what amounted to I guess three hours at it, and a lot of that was on the first wagon as I read, and re-read, did a dry run, re-read and then went for it. After that I ignored them and just built the thing. A second trio would definitely be faster.
Today was a washout and I had less than an hour on them, and the next couple of days are going to be iffy, but I'm hoping that an afternoon's worth of work should have all three ready to paint.
In full uninterrupted flow, and a long day at the bench, I suppose half a dozen could be made ready to paint - glue drying time aside.