I was a rock climber and high angle rescue long before I was a sailor, and all the stuff that sailors do going up and down the mast scares me. There are much safer and more effective ways to do all this stuff. Here's my setup:
First, I use a climbing harness - you can get a cheap one and it'll be safer than any bouson's chair, particularly for work that takes you away from the mast (spreaders etc.).
At the harness, I attach a petzl gri-gri. Normally, it's a belay tool, but it's also perfect for use as an ascender on a boat where you have to manually feed it, but your ascents are short, so it doesn't matter. The nice things about it are that it has no teeth or sharps, so shock-loading it won't harm your rope (it's meant for shock-loading), and most importantly, when you use it to climb, it's already rigged as a descender, so positioning and repositioning are as easy as pie. I use this as my only physical attachment to the line.
Petzl Grigri 2 Belay Device | Backcountry.com
Attached to the line above the gri-gri, and not attached to me at all, I put an ascender with a couple loops of webbing. I use a rescuescender, but any ascender would work, even something as simple and cheap as a tibloc (
TIBLOC | Petzl) or even a prussic (
Tying a Prussic Knot.). The loop of webbing should hang down far enough that when the ascender is at the center of your chest, the loop is at your foot.
All you do is put a foot in the webbing loop, push the ascender and loop up the rope until your knee is bent, stand up in the webbing loop which creates slack between the gri-gri and the ascender, pull the slack through the grigri, sit down in the harness so your weight is on the grigri, and repeat. When you want to come down, you just remove the ascender and rappel on the grigri which is already set up for that purpose.
You don't have to secure the end of the line you are climbing, so you have the freedom to swing around and go out to the spreaders or out to the fore or backstay, you're completely in control - not relying on someone else to hoist/lower safely. You're using gear that was meant for exactly this purpose - not repurposed sailing gear that was never meant to haul live bait up a vertical work environment. And, the climbing harness is much safer than a bouson's chair (if less comfortable) - you can stretch way out in it, even go horizontal or upside-down, and not worry about falling out.
