The boat cradle turned out to be a bit more time-consuming to assemble than I had anticipated. Not difficult, just time-consuming.
Once we had it put together, it actually fit the trailer pretty good. As you can see, I elected to use only four of the six stringers I had cut. These should provide ample support for the boat for the kind of use it'll get. We'll finish the boat while it's on the trailer, then tow it to the lake. After that the only time it'll be on the trailer will be for storage. By the time we get around to wanting to take it anywhere, I'll have taken a stab at building a different trailer; I have a few ideas I'd like to try out.