I recommend you divide the panel into two parts:
- What says in the airplane
- What comes out with the panel
On the RV-8 and RV-10 the stock Van’s panels make this easy. The RV-8 has side wings to mount breakers and switches. The RV-10 has a lower apron for these. This stuff, along with remote XPDRs, ARINCS, Radio, EMS modules and such are things that stay in the airplane. Once the removable part of the panel is out, all these have easy access.
For the RV-6 and 7 you can modify the panel to cut the bottom off and add this lower apron. The RV-14 requires more creativity.
The majority of panel wiring is then the interconnected stuff between the TSO GPS navigator and audio panel, along with wiring to D connectors to the rest of the plane. The EFIS displays are all on a D connector, so wiring to the rest of the stuff says in the plane when you disconnect the EFIS.
Modern network EFIS systems makes this division easy.
As far as the removable part of the panel connections, I use two 25 pin D connectors for everything other than power. For power I mount four breakers on the panel (for me two breakers for the GTN-650, one for the audio panel and one spare). Power to these breakers is via a single molex plug (or whatever plug you like that can handle the current). These connectors are easy to access once the panel screws are out and the panel comes toward you a few inches.
Do this and you will never again be on your back with your head under the panel.
Carl