Nicky
I've been thinking about this a bit recently, because when I learnt how to start using the clip when bream fishing, my catch rate went up a great deal!
Anyway, what I've been thinking about is the fact that when carp fishing at a reasonable range (say 40 yards) using standard bolt-rigs and 12lb sensor as mainline, I have never had a carp pull line off a clutch AT THE START of the fight - they've always kited left or right. I think this is to do with the leverage exerted by the reasonably long line that's out - any variance from pulling in a straight line away from you is going to pull the fish left or right by its own exertions.
(all you scientists out there, please feel free to tell me I'm talking rubbish!)
So I'm pretty sure you'd find that with 12lb line, particualrly with fish in the 4 - 5lb bracket, you'd have no problems fishing to the clip.
TOWARDS THE END of the fight, that's a different matter. Under the tip, with less stretch in the mono and the fish getting a bit more lively, then even a single figure fish may strip some yardage off the clutch. I'd be reasonably confidant that it wouldn't take the whole forty yards though.
I've never caught any seriously big carp (25lb+) it might be a different ball game! What I do know is that quite often for me, the hardest fighting fish have surprised me with their size (or lack of it) - and the bigger fish I've caught have surprised me with their fight (or lack of it)
In addition to this, it's not that hard getting the line out of the clip during the fight, as long as you're mentally prepared for it and you've got a couple of turns on the reel after the cast. I've manged this quite succesfully when a carp has picked up a bait meant for other fish in this way: as soon as you feel the extra resistance offered by the fish, you open the bail arm, lift the rod up until you feel the line is tight to the clip. Then you drop the rod, whilst at the same time locating the line in the clip and releasing it. Dropping the rod gives you a second or so of slck to work in. Its important to do this quickly and calmly and remember to focus on getting the line out of the clip. Once that's done, close the bail arm and play the fish. You'll be fishing one rod, so it's important to have either marked the line (elastic stop knot or folded electrical tape) or have marker on the bank that you can then walk the ine out to re-clip. Best not to fish two rods like this as what happens if you get a bite on the other rod while you're playing a fish? Rod in the lake, disappearing....
There was a thread on this site a year or two back asking what the best single piece of advice or technique was you'd ever been shown. For me, its definitely been using the line clip to achieve accurate results when feeder fishing.
I'll get off me soapbox now!