Hi there
This might be unnecessary advice, and if it is, forgive me... however (through personal experience) I have found that a lot of tangling issues when fishing this kind of set up are a direct result of casting technique.
So you may already be doing both of the things I'm going to suggest...
First off, when you cast, you need to feather the line as the feeder approaches its destination - so when it's about half way there, you gently apply a finger to the spool. Not to stop line coming off, but to slow it down. This has the effect of throwing the bait forward and away from the feeder. If you don't do this, the bait travels behind the feeder and is in a much better position to get tangled up when everything lands. Do it right and you'll clearly see the bait landing two foot away from the feeder.
Secondly, it's important to have the rod held up high during the cast. Then when the feeder lands, you simultaneously clamp the feathering finger on to the spool (no more line to come off) and gently drop the rod top. This means the feeder drops down in a straight line, on a tight line (no billowing slack behind to find a tangle). And because the hookbait was kicked out during the feathering, the flow of the river now keeps that nicely away from the feeder as it drops.
Ironically, it's harder to get this right with a short cast, as you have a little less time to go through all of the steps.
Hope I've explained that ok? And like I said, it could be that you're doing all of that already.....