Beware of this if you go down the "cut down" route CliveO.

I cut down an F-one mast after bending it. I didn't realize at the time that most (all?) of the helicoil kits you get leave a little tab at the bottom of the coil that interferes with the thread if you try and have the bolt go beyond the helicoil. They are designed for the bolt to take up the tension before getting to the end of the helicoil.

I shortened it twice before I figured out what was going on...

DWF said..
Axis doesn't use helicoils.

Just cut and retap. But learn how to use a tap first. Taps are easy to break off inside the mast, if you have no clue how to use taps correctly.

No drilling required. The extruded holes inside the mast are the correct diameter all the way through the mast for tapping as-is after you cut it down.

DWF, thanks!
After reading your reply I have realised just how easy it's going to be.
Got myself confused and thought it was a lot more complicated than it is.

BBN said..
Cut a 72 to 50 and taped the holes. No professionell tools in my shed. Works nicely. You have to seal the open parts inside the profil after cutting. Otherwise there will be a lot of water inside. The big compartment is sealed with a plastic part which you can push out of the cut part and put back into the shortend mast. The two small compartments need to be sealed with resin or wax or similar.

Thanks BBN.
Bought a 820mm and cut down to 500mm's.
Worked perfectly.