But - it's not a very large battery, so can't imagine it having much effect on CofG - and (mine anyway) is an Odyssey sealed gel cell so leakage should not be an issue. The advantages of accessiblity, complete protection from corrosion (unlike rear underfloor mounting) and short cable run surely outweighs the potential disadvantages.
Also consider the proximity of the battery to the fuel tank when mounted at the rear. Not a good combination (I saw two fatal fires in Minis caused by this positioning) IMO.
Nigel
