Don't understand the dry powder use for applying formica over ply.
I would use silica thickened epoxy resin on the ply, or 3/4 oz glass mat sheet, after prewetting ply out with straight resin. Then weight it a bit or clamp it. Router the edge over. Some pieces are very thin I think 3/16 or 1/4 inch, toe rail is heavier. Just wish I could buy the stuff as it was original.
I made an instrument panel out of 1/8 inch polyester board and bonded a piece of wood grain formica to it, of similar grain as Grady used , a bit darker. This was for the yamaha multifution gauges.
Initially I did it in black starboard, had a fabricator cut the panel. The black starboard didn't look good for the yamaha gauges, ripped it out and did it over in the wood grain formica. Looked better to me.
Until I get the weathered duratrim done in the cockpit, liberal coating of Penetrol will have to do.