Hi there !
Got my personnal best leather carp at 44.50, spot which seems to be pretty good for leather, mirror, grass carps (barbels still active).
Clip: 25m with 2m40 depth for float
Rig: waggler rig
About the spot, on loop rig mussels&fruits 16 boilies are decent for mirror and leather carps, for barbels too, even for some tenches.
Go for size 20 if you want bigger specimens, but it will be slower.
The sandwich cream mango 20 + mussels&fruits 20 works not bad too.