Stumbled on this build. FWIW I think you got this right. A quality wooden trailer build is essentially a wooden boat upside down on a trailer platform. I have built a few plywood boats over the years. Using similar methods and not even as high quality wood as you, I still have a little 13 foot jon boat that my son and I built 13 years ago and it is going strong. Best part of your build process is that in case of seal failure and water damage to the wood (which takes a long time of neglect), you can cut the offending section away replace and epoxy/glass new piece in place.
Well done, and of course, I appreciate the graphics as well! Semper fi.
John