I often use larger leads than the "accepted" norm - for instance, at the moment I'm using 3.5-4oz leads routinely. I have chosen the lead size to suit the angling situation that I'm in.
my last water was tiny, approx an acre, a lovely dinky estate type lake, with a good head of carp to 35lb where the angling was up close and personal. A lead on their head was the kids of death. So I would often use leads of 2.5oz. These were flicked into the margins or lowered under the rod tips. I wanted a lead with enough mass to ensure the hook set properly on bolting, yet minimise disturbance when casting. However I did find towards the end that the carp were used to dealing with leads in the standard 2-3oz range and were often getting away with it. So I went up to the larger 3.5-4oz range but flicking them into the bankside foilage above the spot and lower them in by hand. That upped my catch rate as they weren't used to seeing those leads or dealing with them.
Another little trick I used to do was when the carp were stacked up in the narrows (the lake was triangular in shape) they would be in the narrow bay in numbers, the narrows were covered by 2swims that didn't really produce, even if the carp were in the narrows as the water was shallow and placing a bait in the narrows just spooked them out into the main body every time. I would fish the swims to the mouth of the narrows, placing baits quietly along the patrol routes they used to travel in and out of the narrows, then purposefully cast a bare lead into the narrows which made the carp drift off out of the narrows, along their patrol routes and over my baits... Caught every time!
My current water is a largish deep windswept pit that suffers from undertow dependant on wind strength. I find the bigger leads help me feel for a drop in the deep water, as well as in the wind and undertow - as well as being larger, it's easier to keep a direct line to the lead without moving the lead or allowing the undertow to pull the lead off the spot.