I have tried the double jigs, for me it's to much trouble. I like to run a single jig of 1/32, 1/16 or 1/8. I have not longlined with more than 40' of line out with most times 30' working the best and have fished with as little as 10' of line out.
Like already said, you have got to spend the time on some flats and take notes on the depth your jigs are running. Different heads will run at different depths and different body's will run at different depths too. Lots of good fishing longlining but you can only learn the basic set up reading about it. You have to put in the time on the water to really lean how it's done or what works for you. Good luck, it a lot like pulling cranks, you going to love it or hate it!!
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Ascend 133X 13' - MotorGuide Xi3 & Mercury 4