For Dave M., do you mean double nico (nickel-copper) sleeves? If not, I don't understand what you mean by double thimbles.
As for the double nicos, that used to be the standard espec. on hang gliders (I'm a sailing and hang gliding rigger btw) but when testing got better it showed the double nicos made the terminal too stiff, and increased wire fatigue in the area next to the thimble. On the length thing
if you take very careful measurements you can figure out how much length you lose going around the thimble, I have a whole chart I made for how much wire to cut to get the right finished length. Especially with loaner tools make sure to use the go gauge, which is a piece of metal with slots for the different size nicos, and if it won't fit in the slot it isn't compressed enough.
For QB2, don't use 7x7 or 7x19, both are too stretchy. As for the synthetic rigging, it can be a real pain to get symmetrical, and on the big boats they usually have a hydraulic come-along that hooks into the rig for adjusting the lashings.
All in all, it's hard to beat rotary hammered swage terminals, but if you do Kearny swage (has two rotating dies that draw the fitting through) most places do a second pass after rotating the fitting 90 deg. to flatten off the "wings" that form after the first pass, but that's shown to over work harden the fitting. If you got bucks you could also do a Norseman/Staylok type screw together terminal, very simple to do and very low wire fatigue during assembly (these are the ones you should fill with 5200, but on a regular fitting I use Lanocote).
Just for reference, my old shop had a rotary hammer that could do up to 1.5 inch wire, and you have never had fun like having the terminal stick in the die, the flywheel keeps the machine turning long after the power is shut off, turning the wire into flying jumprope of death, literally beating holes in the walls and smashing out the overhead lights until it slows down....