Hello Torgeir - thank you for taking the time to help.
I have also tried another method. This is explained below.
First, I model exactly as I would like to print. A hollow tree with 1.2mm wall thickness and cylinder cut from the bottom. See first picture below.
Add the STL to Cura, set infill to 0% and slice.
A very similar result is produced. Any ideas here? Maybe there is a settings I need to turn off in Cura?