Tigger, do you treat the line at all to make it float?
I recently spooled up a centrepin with 8lb sensor in the vain hope that I was going to connect with some barbel. Never managed to hook anything with it but it was really hard going - partly because it seemed like the line wanted to sink all the time which messed things up a bit at any distance, but also because the line itself seemed to behave really badly on the reel, lots of bedding in and small tangles. I took it off and put 5lb bayer perlon on and it's now behaving much better....
Incidentally, I'm a massive fan of daiwa sensor, it's the line I use for all my waggler and bottom fishing.