Before you remove or seal the CB trunk, you would be wise to consider the effect on the resale value of your boat.
Many of us (at least in my case) ignore lowering the board out of laziness. Performance is effected, but when day sailing, I don't care. The effect on performance is shown by the differant PHRF ratings for a P36-2 fin keel and a P36-2 CB. It is around 10 seconds per mile if I remember correctly.
I remember several articles or comments written by the late Bill Shaw on the proper position of the CB depending on the wind velocity and sailing angle. These may help you understand better the use of the CB and change your mind about doing away with the CB.
If you are set in doing away with the CB and don't mind spending some money, changeing to a wing keel will not change the resale value and should not effect the performance relative to the CB. (Both have the same PHRF rating in most fleets). My notes say that the foundry used by Pearson for these keels was Seaboard Foundry. They may still have the patterns for the wing keel. The bolt pattern for the CB keel and the wing keel were the same. During Katrina, Rita and Ike, several P36-2's were destroyed. You may be able to find a wing keel from one of these unless they have been melted down for the lead.
Dave
s/v ARIEL