Thank you Dave, for your quick answer!

To be sure I understand, would it be like in the little mockup here attached?
Then the "loop" would have to be long enough, with the top half-hitch far up so as to lift as vertically as possible.

My masts have no fittings, they are 100% flush. Note that I haven't yet taken the time to remove the fabric protections (I suppose what you call "coats") to see what was underneath.

Hello to everybody!

China Blue being at the moment on the hard, I had some work to do on top of the front mast.
Although I have been able to be lifted on top of the mast using the sail halyard, it is very difficult to reach the very top with my stretched arms and no way to look at what I'm doing, together with that skinny mast wobbling a little too much for my peace of mind while I'm up there.
Besides now I need to replace the front halyard shackle on the mast crane, which makes it even worse, having to disconnect my harness from the halyard and try to hang from somewhere else.

Which comes to the core of my question: how to you sling that kind of mast in order to lay it down and reinstall it, knowing that
1) it has no spreader bars to stop the sling from sliding up, and
2) its tapered shape makes it even easier for that sling to slide up.

The yard's boss examined the problem and eventually refused to try.

All your ideas are welcome!