I already had boxes of two different kinds of coffee stir sticks for crafting purposes, and the smaller of the two was nearly identical in size to the planks depicted on the printed cardstock deck that comes with the Skycoach.
The first thing I did was remove the cardstock deck. It is designed to be removeable, as both sides are printed (one with a bold 1" grid, and one without, though the plank lengths provide a subtle grid regardless). Then I traced the cardstock deck a few times to make some templates (I really only needed 2, but it never hurts to have extra).

I also traced the location of the underlying support structures of the plastic hull, as I would need for the bottom layer to clear that. I then started laying the bottom layer of my structural beams, measuring, cutting, and sanding the edges of the cuts as I went. I glued these bottom layer beams directly to the cut-out template with white PVA school glue.

Then I began measuring, cutting, and sanding the crossbeams, keeping in mind that my template was actually just a hair too large (the pen can only get so close when tracing the original deck).
If I had kept my whits about me, I would have placed the crossbeams a little more regularly (centering every half-inch), but I have a toddler that I was having to partly watch, so even though I'd had that idea already... it didn't quite happen that way until I had worked my way down almost all the way to the stern.

It is important to get those crossbeams centered on every inch-mark, because that's where you are going to meet up the ends of the planks. I ended up having to put in a few extra narrow joists along the way because of this failure, but it worked out in the end.
I affixed the crossbeams to the bottom beams with Aleene's Tacky Glue, which is a much better product for this purpose than white school glue. Once that had all dried firmly, I peeled the template off and test fitted the structure into the Skycoach.

I then started measuring, cutting, and sanding the thinner planks, again sanding the ends that I had cut, to make them true, smooth, and nice looking. I tested laying out my pattern, then did my best to lay the first two rows of planks with their shared edge making the center line of the deck; I think I did a good job of getting it as centered as I could.

Then it was a matter of affixing the planks with tacky glue, and sanding the curves into the leading edge with a power sander after every row or two, and test fitting it each time.

This is how far I got by the end of "day 1" (keeping in mind that this was sporadically worked on through the day when my son was napping, etc.)

The next morning I continued on, still slowly shaping and test fitting as I went.

I was looking like my planks were going to be off-center in the end, but it was really just that part of the under structure crossbeams weren't centered well (it also didn't help that my Skycoach hull is slightly warped and twisted... Any replacement deck you fabricate is going to be uniquely fit to any individual ship). There is a slight gap to the rear left edge of the deck, but that has to to with the twist in my Skycoach's assembly, and my desire to make sure the deck had loose enough tolerances that it would remain easy to insert and remove.
Here is the deck's "finished" assembly, leaving the gaps that are present in the cardstock deck. In the end my planks were pretty well centered as I had intended them to be.

I wanted to leave those gaps in the deck, so that I could still utilize the ladder and gangplank that came with the set.

However, I also wanted to make some inserts that would slide into the gaps of the crossbeams, and fill those gaps in the deck for when I didn't feel the need to use the boarding accoutrements.

I think they turned out pretty well.

I obviously still need to paint or stain the deck. I know that making actual wood appear to be wood when painted to look like wood is actually fairly difficult. As such, I think I may attempt to stain it instead. I'll try some stain on some scrap pieces of the same coffee stir sticks to see what colors and shades I can get. I'm hoping the wood grain will actually show up a bit, but maybe it won't. I'll post an update once I get that part done.