I have always used the Panckae style 10 Lb downrigger weights but saw a fellow this weekend using one made from Chrome plumbing pipe filled with lead with  one eye at the tope of the pipe .
he hooked his cable and release to the same eye. said it had less blow back than even a pancake and that it trcked over stumps and such without snagging as often as cannon balls...
anyone else use this method??

A buddy uses Torpedo Divers.  Similar idea to your friends but commercially available.

Less blow back than regular cannon balls and you can tune them so they run better for your boat.

I cast my own 15# balls, blow back is not a problem with big balls

Same here.  I made mine with 16 gauge steel fins that I can bend and make them fly out the sides.  I use those on the outside and standard 15lb balls on the insides.  Ran with Cannon Digi-trolls.