Re: Mixing copper and borate wood preservative
I dont know of any application where the two are mixed, so cant help there, but it may pay to look into the effects of your copper based preservative on the metal wrapping of your shutters.
What brought this to mind was my building some gang nail trusses years ago, and learning that we should only use boric treated wood, as copper based preservatives could adversely affect the galvanised nail plates.
There is nothing quite as permanent as a good temporary repair.