I'm hoping 0.6mm won't be that noticeable on the guns, but if it is, I'd sand down the plastic decks themselves. I will just plank the spar deck and the weather decks so guns will be visible and sanding down the trucks wouldn't be a good idea. Another option is to just sand the planks once applied, until they are almost paper thin.
Also, speaking of guns, I just read at the Pete Coleman forum that the Victory had quite a short distance between the lower gun ports and the waterline (much less than what was designed originally), and thus the lower gun ports were tightly shut in all but the calmest weather. So I might leave those ports shut even though I spent quite some time building them up...
Right now I'm struggling with hull weathering. I want to get the outer hull 100% finished and sealed before proceeding with the decks. I darkened the bee lines a bit too much with sepia wash, consequences of using acrylic washes over a matt finish... so I had to add a new diluted layer of ochre, and I'm thinking of ways to weather it in a more subtle way. Maybe just pinwash the planking joints then add some drybrush highlights and vertical streaks (stains) as seen on pics of the Surprise in San Diego. But no overall wash. I'm even starting to hate the molded wood grain and wondering if I should have just sanded it away.