I have seen it done by placing all the switches (and throttle/mixture/prop/carb heat) on a piece of appropriately sized C-channel that is mounted below the stock panel. Nut plates are installed in the bottom of the panel, and screws are inserted through the top flange of the C-channel from below to hold it in place. Holes are required in the bottom flange of the C-channel to allow a screwdriver in to drive the mounting screws.
[edit] Just noticed this was in the RV-10 forum... What I saw was done on a few side-by-side models, 6's and 7's... Not sure what the arrangement is on the -10.