Or is there a way to scratch built one.
Yes. There are cutaway views available to show you where what’s between the outer skin and the pressure hull. Unless there’s some way light could shine from the top of the hull all the way to the bottom I wouldn’t worry about it. You’ll never see it. What’s more important when doing the holes like the ones on the bottom of the Gato (diagrams also available online) is thinning them out from trhe inside so the skin doesn’t appear to be eight inches thick. There’s a lot of piping and other equipment you can show off on top of the hull of a Gato if you’re really of a mind to do so. You’d need the Big Ed set to be able to see anything at all.
While I don’t want to sell I believe I have the upper pressure hull by Yankee model works somewhere.
I can dig it out and take pics / measurements if you need them - LMK
arent there some 3d printed offers at scalemate for pipings around the pressure deck and tower? I ve seen it a year ago or so but it was pricey…
For the U-Boot or any other large submarine such as the Gato I wouldn’t spend a dime on a set like that. Evergreen tubing and some appropriately shaped parts will more than suffice. As I said, you can barely see more than shapes in there. Unless you’re one of those “But I know it’s there” modelers, the juice isn’t worth the squeeze.
I doubt you’re going to see much through those small holes.
You just need to give the impression of something there. Maybe you could form a section of plasticard inside the hull halves? Scrap tubes or even sprue would give the indication of piping. Paint it all a dark colour it should do the job.
While it has not been said I am assuming the question refers to the Revell VII C .
If so then very little will be seen through the flood vents on the hull . Most will be visible through the deck if using aftermarket photo etch or other deck that has true slatted openings .
Here are pics of the Yankee Model Works upper pressure hull . Hope this helps .