I'd be grateful for any views/guidance on this.
The backing plate sits under the foredeck and is a large piece of 20mm plywood. The stem head fitting is bolted to this through the deck by stainless steel nuts and bolts on penny washers.
The wood has softened due to water getting at it, so I want to replace it.
What I propose doing is replacing it with is 5mm thick High Density Polyethelene (HDPE) which I understand is the same stuff that plastic chopping boards are made from.
I am thinking about adding a 3mm stainless steel plate cut to the same size as the HDPE backing pad so that the HDPE pad is sandwiched between the deckhead and the stainless steel plate before bolting down onto penny washers.