I would dump the engine gauges and install a Dynon D10 EMS on the right side.
Then your passenger can have an EFIS, if they are a pilot.
It will probably be cheaper, integrates with the D100, lighter, easier to wire, and take up less space.
Of course, you can always put it on the left side, if you want.
(I started with a D100 EFIS and D10 EMS and really liked the setup.)
One other thing, do not put warning lights on the top. I started with a green fuel pump on light near the top of my panel and at night it was TOO bright.
If you go with the Dynon EFS & EMS, let it manage all your warning signals.
Move your headset plugs under the panel, on each side, and mount them vertically. Save your panel space for use later. (You might have to make a bracket that you rivet to the side.)