Good question. Might as well ask what type of oil should I use. I am just kidding.
As coljar said nothing smaller than 4". You can use a big vise for small work. It is hard using a small vise for large projects.
The highest in a lift was a 125' working on silos at a MFG plant. That was not as bad as going higher than 150' in a man basket hanging off a crane, that had a pucker factor of 10.
I don't like heights at all.
Metal insulation supports are used in crawlspaces. Sounds like what you are looking for. Around $10.00 per 100.
https://www.homedepot.com/p/THEWORKS-16-in-Insulation-Support-100-Pack-BW13G155/301861840