Finish them prior to installing them in the
boat if at all possible. IE; epoxy coat, & then
varnish. And if the strips actually hold your headliner in place, then you'll want them to be removable. Meaning attached with removable fasteners, so that you can pull the headliner when needed in order to run wires, or add
deck hardware with the nuts for same hidden underneath of the headliner.
Also, you might consider using some pretty
wood for them anywhere that the strips will be visible. Such as red cedar, or something with nice contrasting grain (color) patterns. It definitely adds a touch of class to the boat. And you might ask the Mrs. for her input on colors & patterns on this. Both for her taste input, & so that she's a part of making the boat feel more like a weekend cottage, than a guy's hunting
cabin.