Windowed planks only work on the ships that come with the mod due to the limited mod-ability of existing ships

Thank you for the answer and the mod of course :) I was thinking the mod gives you different planks for the stern of the ship ^^

You're welcome, it's a common misconception with custom planks so I can understand if there's confusion. Most modders are hoping the future updates will make modding ships easier both for modders and players.

Yes true, devs really should make modding much easier in Atlas. It makes the game so much better