You won't have problems with water. The regulator itself has it's electronics encapsulated so it's sealed against rain and grit but as a precaution make the bullet connections up inside the tail unit and seal the wire penetration with silicone sealant or a grommet to prevent chafing the insulation. Use some sealant where the wires enter the regulator if it makes you more comfortable.
(Last year it didn't rain here for six months. Sorry, I couldn't keep from rubbing it in)
[Edited on 6-20-2005 by Shazaam!]