Hi James,
Thought I'd give others a chance to chip in.
I presume you haven't fitted the centreboard case yet?
If not then I don't see much point in taping round the slot until it goes in.
Chris is right is saying you can never be too careful, although I must admit I just bedded it down in enough gloop to hold a carrier in place.

What you can't see in the picture is the blanking piece I made to fit inside the slot, just a long bit of wood the right size covered in parcel tape to stop it sticking, it was held so that the case sat right over it in the right place and couldn't move around. Once the epoxy has gone off stick a batten down the slot and give it a good whack to knock it out.
I did line the inside of the case with some biaxial cloth I had lying around and if I was doing it again I might run some tape round the inside join between the case and keelson. The trick is to get a good join without leaving a rough surface to chew the board up.
There is an external brass rubbing strip along the keel and on either side of the case to protect it from beaches and trailers.

Cheers,
Graham