I don't know Cat well enough to give you the scoop on the best locations, but I have made them at Hen Rock several times. I've also had them come up thick in West Cove.
It's not that complicated. There are no absolutes, but I've usually made squid in depths from 70 to 120 feet. (I have had exceptions on both sides of this range, but that range is the most common for me.) I've used the Fluorescent 48 inch "green magnets", I've used the cheapy small submersible lights, and I've used the big Halogens above the water. All will work, but as a general rule, more lights better.
I like to use a small light in conjunction with a larger one so that I can move the small light to lure the groups of squid into my crowder.
More often than not I fill the tanks with squid jigs (rather than a brail or crowder) being used anywhere from just below the illuminated area...all the way down to the bottom...they are where you find them and it helps to try various depths.
If they come in really thick it helps to have a crowder. I made mine out of two twelve foot lengths of Calcutta cane, and some weighted net material. If the squid get thick you drive the netting straight down along the side of your boat and then come up under them with the crowder. Once you have a bunch in you use your brail net to transfer to the bait tank.
A good color meter helps a lot. On mine they look like a blue line on the bottom. When they get thick you see it on the meter in various colors depending on the density.
Bill