Think about setting up an outpost at whatever good swamp you find. Preferably like 4+ Crypts.

When you're ready, sail over the materials you need to set up a Forge+Upgrades there, and some Smelters.

Then you can easily smelt and craft all your iron on the spot, while portaling back to your base when you need to.

This is what I prefer to do, rather than risk bringing massive loads of iron across sea. Then when you're done, if you still feel the need to bring your excess iron home, you can sail it home.