maybe get into the habit of transport a portal with you... 2 red cubes that you find in crypts, 20 fine wood and 10 dwarf eyes. you will need 2 portals 1 at base and 1 in your inventory so when you go on a harvesting run and your inventory is full make the portal GO back to your base unload then return. Now YOU WILL NOT BE ABLE to transport tin (or any metals ) threw the portal but all the rest should be good.