So we are going to be doing some repairs on the hull to fill in holes where we remove Seacocks (the number we remove is still up for debate). Boats like ours were built with Polyester Resins and glassfibre. However, we plan to generally use Epoxy resins for repairs (stronger, less shrinkage). But Epoxy resins have also been both not very safe to use (toxic) and very fossil fuel intensive. Also more expensive. See this guide to making the repairs.
Fortunately there are now Bio-Resins available which are far less made for the environment. The one I’m looking at using is Super Sap. It is quite time consuming to find (and confusing options) and to do so at good prices.
The other area I’m researching at the moment is whether there is a more environmentally better option than woven Glassfibre mat. There do seem to be both Flax and Hemp options (although many times more expensive).