What length of leader is best to use on a sinking line?

I always go for the longest size that you can succesfully cast with. There is no point putting on a huge length if it just ends up in a big pile

for me 7/8 ft is fine. I know 2 salmon fishers that use 1.5ft to 2ft and have good results

I've found that 10ft is plenty long enough but you might want to shorten that in windy conditions.

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I dont suppose you need tapered leaders on sinking lines.

I have a standard leader length of 18'. I'm 6' tall and my "wingspan" is about the same so it's spool in one hand, end of leader material in the other and then three full arm expansions. This gives me the leader and enough spare to make up the two droppers which are 6' apart. I've used this system for a number of years and don't really see the need to alter it. I'll use this on most of my lines. If the wind is a bit tricky or if I need to cast into it, then I'll shorten the leader, but rarely go below 10' except on those hen's teeth occasions when I use a booby fished deep. On rivers the leader is usually around 10' in length, but may vary according to the size of the river I'm fishing.

I always use a short leader no bigger than 5 foot on sinking lines

if you use a long leader the fly will be way higher up than the line so there is no point in using the sinking line in the first place

Anything between 6 inches and 20 feet. I have fished close to the bottom with booby nymphs on an extremely short. I have also hung out smaller flies below a floating booby using a DI 7.

Actually the flies will not be higher in the water or not by any significant amount. Once you have made your cast and allowed the line to sink to the required depth a couple of long pulls on the line will see the flies down to the same depth as the line. If using dropper the top fly will be the deepest as it is closest to the line, but the difference is marginal. You can see this easily enough when you fish a clear water venue and you have fished out the cast and are ready to roll the line forward to get it moving.

Assuming a single pulling fly on stillwater, then I would suggest a shortish leader. The fly may sink slower than the line, depending on the line density and weight of fly.

However the shorter leader will get the fly fishing for longer as you don't need to pull the fly to depth or take any slack out of a long leader (crappy cast) 6-8' length is more more than enough.

With a single nymph I use a slightly longer leader as they are fished much slower than a pulling fly, you have time for everything to sink and fish out the cast.

Get more than 1 fly on the leader then generally my leader would increase by 5-6' per fly, so a 3 fly leader, for me, would be about 16 - 18'

On running water, I've had some good results recently fishing a very fast sinking mini tip and a very short 4' leader with a weighted sculpin pattern. Incidentally this set up also works very well on a steep bank presentation on stillwaters.

In short you should vary your leader length to line density, fly weight, depth and movement of water and retrieve. There is no universal length.

Good luck

taff