Downrigger ball..weight, style?
I kind of disagree that fishing down deeper than 100 is a waste of time. There are days/periods when the fish are there. You can do a lot of damage down that deep. Several trips come to mind when I remember fishing successfully down deep.
My advice would be 12# cannon balls with fins. We used to run 4 riggers, same weight on all (minus balls deep). We only run 2 riggers now, with 12# on both. In my opinion, 8# is bordering on "too light" as currents can do damage depending on depth and dipsy spread. They all work, but 12# are versatile.
I mainly fished with 10# weights. I bought one 12# weight to use when the water temperatures drove the fish deeper than 100’. In 20 years I’ve used that 12# weight less than 5 times. Just connecting the 12# weight was a task I’d rather avoid, that two extra pounds of lead makes your toes look for places to hide in your shoes. Steel toe shoes are good shoes to be wearing when connecting downrigger weights to cables especially if you’re using cannon ball style weights that roll around in rough seas.
If you have to fish at depths greater than 100’ you should probably rethink what you’re fishing for and fish inland for pan fish or bass. Most times getting out to where the depth is over 100’ is at least 4 miles from Milwaukee to the Fibville, in Racine is about 6 miles.
10# weights work great to about 100’. Below 100’ I’d use the 12# weights and as mentioned if you’re using manual downriggers plan on having sore wrists and arms, especially if you change baits frequently.
You can find this style weight on eBay or buy your own mold.