My boat came equipped with a Genuine CQR, 25lb.  So far this has not let us down.  However it's the only thing on the boat which was designed before 1940, so I think I would be safer at anchor using one of the new generation anchors.  The problem is that the anchor locker is not very deep, so it may be difficult to fit a different anchor in. I have found that a Rocna 10kg anchor fits in the locker, but I think it's too small for the boat.  Has anybody tried one of the modern anchors in the P31 anchor locker?