The mast on my Geko was 60′. When Haiko bought that boat, the mast had to go into the container. Haiko is a master machinist, so I watched him do it. He recently topped up my recollection with the procedure.

“As you said: the mast was indeed welded together from 2 pieces. It was done with 2 inner-plates made from the same mast profile on port and starboard.  By sanding the paint you could see the different structure of the welded aluminum.
Three rows of holes measuring about 3/4 of an inch were drilled in the outer profiles and to the welded  plates.
So we had to drill holes of 30 mm through and  around them as the weld is always bigger than the initial hole if done properly.
The mast was cut very attentive (carefully) 3 mm under the weld, to know sure it would part while trying not to touch the inner-plates.
Back in Holland 3 different series of props (nuts? I will find out)where milled 3d for inside as well as for outside.
After welding we still had to do some sanding on the inside. The mast is now demountable in two parts for legal transportation on the road.”