Locations
Original poster here, Thanks to all for the advise. This is daunting and outside my normal skill set. What is the benefit of adding large connectors to the panel wiring? Are you making it so the whole panel can be removed for work? I don't think that is practical in my RV-7 because the sub panel is not removable but riveted in and most of my "boxes" will be attached there. I like the hinged panels under the panel. I did incorporate that into my design a long time ago. Now I have to figure out where to put all the boxes!
Other than Transponder and ELT, what boxes are you all mounting somewhere OTHER than behind the panel?
Sorry this is long and limited to my expertise.
My transponder, com and adsb are mounted to the sub panel. Advanced Control Module and ELT annunciator are on the starboard hinged panel. Backup EFIS batteries, EMS, Alternator regulator & stall warning circuit board are on the port hinged panel. Panels and associated boxes and cables must clear anything above.
Some manufacturers sell the interconnect cables prewired. Saves a lot of work.
ELT and ADHARS are in the fuse. ELT has a panel. I almost forgot about it. ELT also has an annunciator. Both have batteries to replace at designated intervals. If you have a B&C alternator, there's a regulator box to mount. Access is handy should a voltage adjustment be required.
Make a list of every box. Put sample connectors on each box, one at a time and measure. It's not just the foot print of the box. The connector and cable need space. Consider how you will take that box out if necessary. Orientation of the box matters too when it's time to work on it. There are connectors on ends of cables but usually not many in between. Nuts & bolts or screws & nutplates. The latter are easier but installing nutplates laying under the panel is not fun. Neither is nuts & bolts so pick your poison.
If you have breakers, consider all that wire is carrying power. You need the correct breakers and wire gauge.
How will you pull the panel? Does the controls quadrant come off? It helps to practice and consider what connectors have to be removed to pull the panel.
That's one plus to electronic breaker boxes. Switches are connecting to ground. No power. A harness can be made to disconnect the entire bank of switches. Wire is smaller guage so a d-sub can be used.
Lights need power, switching and some have controller boards.
AP servos, trim servos get connected to the electronics. AP servos probably use a manufacturer's harness. Trim servos can be wired with Ray Allen trim wire. Colors are standardized among many manufacturers.
Flap motor needs to be connected. Power at least. Most builders add a position sensor. The new PH Aviation motor has one built in.
Stick grip controls have a harnes(s). That sort of includes the mic and phono jacks. Tosten grips are pretty well documented. You need to research which pins on the electronics are utilized.
O² may or may not be built in.
CO detection.
Antennas
I can't think of anything else.