Finally got around to installing the etrailer wiring harness. Printing-out the installation instructions for the Honda harness (way more involved!) from a Honda parts/accessories supplier, helps you locate the various clips, tabs, snaps and bolts.
But you do not need to remove the whole side panel. The rear floor board and the hatch threshold need to come out, including the two tie-down loops. Then pop loose the rear edge of the side panel and about halfway along the top edge. Gently (g-e-n-t-l-y) pull the panel out just far enough to look in to locate the white plastic plug. You can reach in and hook-up the harness' plug without much trouble. Make sure you have it lined-up the right way. Snap it together. There is a ground screw conveniently located a little further to the rear - there are several ground wires on it already so make sure you get them all back on.
Use the provided double-sided tape and stick the electronics box somewhere where it won't be in the way of the side panel. Route the harness out the bottom of the side panel and into the wheel well. Snap all the bits back, and you are good to go.
BTW, I didn't use a panel removal tool, just two putty knives. The special tool would certainly make the job easier but I got by with extra care and without the tool.
OK now, let's tow something!
pete