Usually you have a big swivel of some sort where the cannon ball connects the downrigger line.
If you are running wire line you need to isolate the ball from the wire electrically.
Scotty makes a plastic swivel/clip that works great.
If for any reason the ball rotates, the swivel stops your line from twisting.
I use 12lb balls......most of those come with a built-in fin.
I wouldn't worry about adding a fin if you have a good swivel connector.
You don't need to electrically isolate the ball if you are running braid.
I don't see why you'd need a rubber snubber on your downrigger line for either wire or braid.
I've never used one ever....and never had a problem.
Neither wire nor braid stretches.....and it's never been a detriment to me..
In fact I think the ball bouncing up and down on a snubber whileI was trolling would do more harm than good.....just my two cents worth...
IMO...the ideal world would be to run a separate black box for each wire. IMO, the fun starts when you try to run two wires at different depths off one box.
If you are running one line at 200' and the other at 100' it is impossible to get the correct voltage to each line off one box.
With the box "on" you lose 1/2mv for every 100' ft. of depth.
So if you fished 200' you would need to set the dial at .70 to get .60 at that depth.
Problem is your other line is at 100 ft......so it's getting .65 which might be too high for "Nooks.
And.......it'll be foggy a Friday before you get EXACTLY the same surface test reading with a meter on both lines to find out what your "normal" is.
One side will invariably be a shade hotter or cooler than the other side.
And now you've got to figure out how to calibrate this whole shmoo off one box.
Did I say "spastic hair-pulling sh*t-fit on the water"?.......
