this is an outstanding build and I'm always happy to see some thorough research
I have 2 observations at this point: The first is the frame; with my pack the 2 lower seed trays are actually pretty much squeezed between the lower bar/curve and the bar on top. As a matter of fact, I had to bend the frame to a certain degree in order to make them fit between the two. This means if you still have some space left on the top you probably have to lower the upper bar.
Besides all those faboulous parts, the exhaust port does stand out a bit. It needs to be at least 1cm if not 1.5cm wider. I'm not sure about the other proportions but it might help if you could put it on the seed tray next to the bottle&cap to see how it fits lenght-wise.