I noticed on some videos that people have a set screw where the front of the boom rear on while they hook up the pigtail to support the aft of the boom.
I don't know what the set screw is all about. The pigtail works by attaching it to the boom as you drop the main. It can get a little awkward and frustrating if you can't bring her head up into the wind. Being able to use the anchor is a big help. Let her swing around into the wind, loosen the sheet, connect the pigtail, drop the main and the boom stays up for flaking. If this isn't a good idea because the wind is too strong and squirrelly, drop the main, then pickup the boom and attach it to the pigtail. That way, you hold the boom at a good height for flaking the main. Not my favorite way to hold the boom up, but it works ok.
I also have another cable along with the backstay that I don’t understand what it’s for.
Please post a picture. Where does it come from on the mast, top, couple of feet down, below the spreaders?
Does it move like it's on a pulley or is it fixed and tight?
Is it all cable or is there a rope spliced on?
It could be a halyard or a topping lift, a lazy jack, or even another stay, those last two suggestions are a bit of a reach.
-Will (Dragonfly)