I use a 5kg Bruce type anchor with 10m chain (plus rope of course!), which is brilliant in east coast mud and certainly fine up to F5 and 3 knots tide. I even had one occasion this year when this little chunk of metal was really not willing to break out! I hook the anchor over the pulpit (I have covered this with rope to stop scratching the metal) and then tie down on the stemhead and the anchor is light enough to manhandle.
I have a 15kg Danforth/5m chain for use if more severe conditions are expected which lives in the cockpit locker.
What IS infuriating is having to feed the rope and chain down the tiny hawse pipe! I am considering swapping the anchors/warps over, and keeping the Bruce plus warp in a bucket in the cockpit locker but still using it most of the time. Providing I don't drop it all overboard.....
In passing, I would also comment that the 21 is very fidgety at anchor where tide and wind are not in agreement, and I always leave the plate down and lock off the tiller amidships (maybe using the autopilot, switched off) which makes things much more comfortable.
Phil Hanley