This discussion makes me feel better about all the gear i take up with me. I was thinking I looked like a dufus, clattering around decorated with anodized gear like a Christmas tree compared to the bare bones shinny style climbers. But I didnt start tree climbing again until I'd learned and practiced switching climbing lines and descent gear at low level, and then practiced that at height, before tackling the mast. Always have at least a plan B and C. IMO, a mast is harder, in that trees have bark that grips lines well, masts are slippery. Trees have generally wide angled forks and branches that can help you, while masts have thin, close angled shrouds and stays that always seem to trap you.
I also appreciate the comment about not trusting the turning blocks at the collar, I totally overlooked that.
If I have a helper, they follow me with another halyard on a winch as backup. If not, a backup line clipped to a webbing loop that is cow hitched around the mast and fastened to my climbing saddle, and can be pushed up as I go, unclipped and re hitched above spreaders, etc as needed. It isn't a completely hardened attachment and likely to slip a bit if catching you in a fall but then plenty of injuries can happen from the shock of arresting a fall, and the main objective is to not take the loooong fall, so I think slippage for the backup isn't necessarily a bad thing. I'll take a broken rib or nose over a broken neck.
FWIW, I climb on a Hitch Hiker 2 ascender/descender with foot and knee ascenders, and use a Petzel I'D S as my backup descender, which can also be rigged at the base (base tie) so if unconcious, I can be lowered from there, without anyone having to climb up to rescue me. That requires an extra long rope, so theres enough to go from the deck, up through a pulley attaced to the halyard, back to the deck, and enough after that for lowering, so 3x the mast height.
If incapcitated, a rescurer can lower you by operating the descender's lever. The same precaution could be done with a deck winch, just takes a longer rope. And, then you could still take a backup line and descender with you so you could also self rescue from a main equipment failure.
An advantage to that could be the possibility to also raise an unconscious climber up off an obstruction with the winch, an otherwise horribly complicated task.
More FWIW, for scheduled work, I climb on a decent entry level saddle for the comfort and security. For emergencies, I carry a rock climber's version on the boat.
Last FWIW, fear of heights is a big deal, people can need rescuing from getting frozen by it. Having real, properly rated climbing equipment is essential. Honestly, it would take a tow truck to pull me out of a tree and I count on that. Practicing with it low and slow, long before attempting heights, and doing it often enough to be proficient in its use is also required.
Fear is crevice corrosion for the brain and things in there will snap if you haven't worked on your mental game as much as your technical one. You need a mental toolkit handy to sort through when something unexpected happens, anxiety starts to creep in, and your basic self assurances suddenly don't cut it.
Unless you're one of those fearless folks that are unperturbed by anything, in which case I dislike you already.