I gave up entirely and cut a large rectangle from the sub-panel for my radio stack to go into, then made a beefy box structure with aluminum angle for the trays which attaches to both the panel and the subpanel (I had to lose a complete rib panel-to-sub-panel on onse side because of EFIS placement).
I think this is one of those areas where you just have to modify the structure as needed to make room for whatever equipment you have. Some folks have cut off the aft portion of the rib and relocated, or made new ones, to tie the panel to the sub-panel.
I repositioned the canopy release in such a way that it was downward, behind the subpanel, but eventually that got in the way, too, so I ditched it entirely. That's a decision each builder has to make on their own...I'm comfortable not having one.
Oh, and if a fit is tight, but not *too* tight, you can get various form factors for D-subs that have the wires coming out of the side or at an angle from the side. Check the usual sources for connectors.