Yeah, I save that thin veneer from cigars too but it's more useful for making square or wide areas of wood than it is for planking because it's useually too thin for planks by itself unless you stick to something (like the plastic you suggest) and then it's extremely difficult to cut it in a straight line for planks.
However, if you do decide to use it for planks, cut the plastic sheet into strips first because it's easier to get straight lines, and if something does go wrong (the plastic cracks or the cut goes off straight) then you haven't lost a piece of veneer. Then glue the cigar veneer to the plastic "planks", making sure it's oversize, and trim the edges with an X-acto knife or scapel.
I use precut cherry wood planks that I get from a company called Lee Valley in Canada. They're very striaght, very thin, they take stain and paint well and they have almost no grain so they look great for wood decks. You can order it online at
http://www.leevalley.com/en/wood/page.aspx?p=40840&cat=1,250,43217Unfortunately, the cost of $23.50 CDN might be too much for the small amount you'd be using on your boat. Each strip is about 24" (61 cm) long so you'd only need about 2 strips. Maybe there's some way we can work out how to send them to you?
On the type XXIII itself, the deck is really just a few planks bolted onto frames straddling the PH. Keep in mind that in real life, the planks were spaced a few cm apart to let water through. They were raised above the PH slightly also, so water flowed undeath them between the deck and the PH.
You're lucky, the type XXIII is the easiest one of all the U-boats to make a wood deck for and you're also correct that making the deck out of real wood looks great and adds a lot of authenticity to your build.
