I lifted the big fir today. Dug out some top soil and loosened the rootball a little. Filled the bottom of the pot with leca to raise the tree to the rim, slipped the tree back and filled the spaces with moler. I cleaned the low trunk and top roots with a water jet. I'm happy with this trunk! It will stay like this for the rest of the season and I will trim it in autumn to make it smaller for winterstorage. Surface looks a bit messy at the moment but it's mostly roots that were growing upwards and they will be eliminated eventually.