After a number of failed trials, I decided to take the matter of the design in my own hands. This tree stands 288 mm tall and was printed from the 80 mm main .stl only. I scaled the x and y 200% and the Z 360% . It uses 3 perimeters and no infill. put as many bottom layers as you wish. I used 2.

Scaling the xy by 2 causes the slicer to put the loop in the g code out and back to the trunk and results in a tighter loop. You can leave the retraction on if you wish . I printed this with PETG. Scaling the Z causes the slicer to create more branches vertically. You can keep the Z scaling the same as the XY if you want but I like taller thinner trees. You can scale the XY anything you want as long as you increase the layer width to go with it (220% = .48 width.) but you will have to scale the layer thickness too to maintain the 1.2 ratio.

Printing in this fashion solves a lot of problems.
Printed on an Ultimaker clone 400x400x300 with an E3D V6 hot end and a Bondtech BMG extruder.

I am currently printing the 120 mm version in the vase mode scaled 200% and it appears to be going well. I will add more pictures as I try different variations.

Update:
The second tree is the 120 mm main .stl printed in vase mode after scaling 200% on all axes. No cooling and perimeter speed was 60 mm/sec. Print time 4 hours 30 minutes and 34,000mm of filament.

Update:
Once the XY is scales at least 200% these will print in vase mode. Just remember that the 80mm version has the branches of a 320mm tall tree when the XY is scaled 200%.