John,
We keep our 235 on a swinging drying mooring at Woodbridge and have had no problems with the "drying out" bit - it is relatively shelterd although wind on tide can set up a bit of a chop that can make boarding a bit of a challenge. We keep about a foot of keel down and raise the rudder. However, the boat does sheer about quite a lot in the fight with wind and tide when it is floating. So much so that in the first year the mooring that had taken my previous boat (that was twice as heavy) failed. In order to counteract this excessive swinging, we have tried several things:-
(1) a bucket (with large hole in bottom) streamed behind the boat. This seems to work a bit but the bucket only lasts a few tides and gets squashed or otherwise breaks
(2) a car tyre streamed behind the boat - this works partially but has the disadvantage that the tire needs to be taken on and off and gets extremely muddy; we don't do this anymore! Others use a half tyre which might be better (as it might be self cleaning.
(3) Twin mooring ropes to the port and starboard cleats/fairleads and not over the stemroller - this dampens the swing more than a single mooring rope but not that much more. Some people say that each rope should be taken to the cleat opposite the fairlead - we haven't noticed that it makes a difference.
We haven't yet tried a proper "canvass" drogue or using a short immersed rudder. The latter might also be useful to steer the boat when motoring in shallow water with the keel is raised. Reducing the windage, i.e. lowering the boom and sprayhood (we haven't got the latter).
If your boat doesn't dry out and you can be satisfied that there will be a good depth of water at low tide,I would leave the keel and rudder down - the boat is much more stable. You may get fouling on these but the hull will get fouled anyway and needs to be cleaned regularly throughout the season unless you use eroding anti fouling (and even with this sometimes). Leaving the keel up is really only for sheltered waters. In the great storm of '87 boats with raised keels, like the 235, moored 6 mile from the river mouth inland turned turtle and sunk - those with keels down tended to survive.....
Hope this helps.
Regards
Chris Cobb
235/48 "Tarakihi"