Sure, you got it.
I'd be surprised if there's a deck made for that model, but I could be wrong.
I don't know a thing about Galleon decking, but it was probably fairly wide. For simplicity sake, since the model is 1/96, a 1/8" wide strip would be a foot. I think that would look pretty good.
I think planking decks is fun. It'll be a big plus on your Victory, even just the weather deck. This is a good place to practice.
You can buy basswood from Blue Jacket or probably Model Expo. The general principle is that the planks start and stop on cross beams, and the cross beams occur at the frames, so it all has to line up. The frames are where the gun ports "aren't", they bracket them. So take the plastic deck and accurately draw a centerline down the middle. The make evenly spaced lines side to side where your deck beams would be. A guess would be on four foot centers, which is 1/2" to you. Draw those lines across the deck, starting from the bow to the stern.
I start planking in the middle. Ships typically had a wider plank down the center, a king plank. I think you can ignore that here. Lay planks along one side of the centerline. There'll be lots of interruptions from hatches and masts, but cut little pieces to fit.
A full plank would be 16 feet to 20 feet long, 2" to 2 1/2" for you. A rule of thumb is that the ends fall in a regular staggered pattern, and the pattern repeats itself every "X" number of planks, "X" also being the number of frames the plank spans. In other words, if your plank is 16 feet ( or 2") long over frames spaced every 4 feet ( 1/2"), thats four frames. So the pattern repeats every four planks.
It'll make more sense to you once you get going.
I hope that helps.
Bill