Probably been discussed before so apologies.
I've got 2 90cm masts but want to cut one to 82cm.
Had anyone done this before? cutoff saw retap holes.
Does anyone know if the black inserts that seal the holes be knocked down with a hammer and podger.
How long are these inserts I assume they don't go the full length.
Maybe someone wants to swap a 90cm for a 82cm
Thanks for any info.

Cut and tap. The "drill hole" is in the extrusion. Just do the plate end and fill/seal with 5200 marine sealant - not just the holes fill the whole gap between mast and plate too and get it in the screw holes (lets be real its 5200 you'll get it EVERYWHERE) I like to pre-assemble and then tape off where the 5200 shouldnt go then i can go crazy and not worry about it.

Yeah just cut and re tap you can also get a bit of flat bat bar and drive the rubber seal in deeper before you cut , easier to cut the fuse end .

Yeah don't snap the thread tapping tool like I did then it's cactus!