Hi Rob
Sorry I am with Marc on this one, having fished with 30ft leaders & 6" of fly line
in the South African Streams several times over the last 3 years I can tell you it
is not leader weight but technique that lobs the flies forward.
The idea is to have as little line drag as possible so as to present a realistic fly.
Casting or more truthfully lobbing up stream & fishing the pockets as the fly dead
drifts back towards you. Fishing either Nymph style or dry fly. Largest tippet being 5X.
Excuse the fat git in the picture but you can see the fly line is inside the rip rings & there
is not slack line, basically keep contact with the flies at all times & lift into any stop if using nymphs
or any submersion of the flies if using a dry nymph combo.
If I remember rightly I took 5 or 6 fish out of this short stretch of water.
Alex