I just winged it Pete which is why it took so long to build. There was a lot of trial and error, thinking, figuring, measuring and adjusting and it is still going on. 
I used photos of the real deal and Dan Gilchrist turned me on to a design program that showed top and side angle computer drawings. I used this to get an idea of the layout of the pieces and then used selective compression to make it work for me. It was called Autodesk DWG Trueview 2025. Schnabel 256 colors
I agree with you Pete. You NEED one of these. 
I just finished a video featuring the build up, testing and run round the layout. I’m going to post it on the Video tab here.