The aim when rig tying is to have a good hook hold, often with the lower bottom lip, or in the scissors of the jaw, where in both cases you’ll achieve that goal.
However, there are many places within the mouth where good hook holds can occur and taking these into account could help to land more fish.
The lip is a very good place, but to be consistent, the rigs need to be very effective in that small position, namely as the bait is leaving the mouth, the hook must catch hold. Any faults in the rig tying and the hook can miss the target.
Similarly with a Jaw Scissor position, the fish needs to be moving away and the weight sufficient to draw the hook into the jaw joint.
The fish is taking the bait into its mouth to assess if actually food or is accepted as a food or with other food items.
In each of these cases the bait and hook along with it, moves to the back of the fishes mouth, almost to the throat if the fish is still assessing or into the throat if eating. Additional debris and smaller food items are often ejected through the gills and not back out the mouth, this leaves the bait and larger particles deep in the mouth. It’s at this point that the fish may become spooked when the bait does not act like other particles in its mouth or the rig straightens and halts the baits further travel or consumption, either way this can lead to the fish ejecting the bait, at which point the anglers prowess at rig tying will become evident.
However, the point to this is have you considered this process and allowed your rig to function as intended in relation to the Carps size.
A small double, or mid-20, such as in these images, with a 2 inch Choddy type rigs seems pretty in tune, although perhaps longer ones might have gone in deeper, but the result will likely have been the same.
Consider though a 40, 50 or 60lber, the sizes and depth of the fishes mouth should be a major consideration when tying your rigs, because a 2” Stiffy just won’t cut it.
Perhaps that’s why so few big fish are not caught on these more intricate rigs, they just haven’t been scaled to the fish.
How often have you seen an 8” Chod or 20cm Pop-Up fished? Perhaps now’s the time to start scaling up the finesse rigs designed for small water carp and take advantage of the specialized rigs mechanics but to scale.