i think its a better idea to get a new antenna mast off ebay. if you still don't want to use the antenna at all anymore, just unplug the power from the antenna motor when the antenna is all the way down.

the problem is if there are broken teeth inside the antenna motor, you have to take it out, open it up and remove them. its not *that* bad, but i had some problems with mine... the mast was stuck in there. you should see what i had to do to it to get it out............

a bolt and a rubber plug would look pretty ugly