Over or under balanced both work, now after reading Yonny's comments I think it could work against us at times also. Slow sinking, I'm expecting the bait to move if stirred up and act more natural, like the rest of the freebies, That's always been over particles though. I don't balance boilies, or it very rare......Pop ups I will over weight ... I guess that's the same.
I watched swans kick up all types of baits I'v put in , in deeper water than they can reach. Makes me wonder what actually happens when fish stir up baits...though these days I'm always wanting a resetting rig as its hard to keep a rig in the water for long with the bird(thug for) life