If I understand the problem, you've got a cartridge-type BB on which the position of the bearing cups is fixed relative to the spindle. So for the spindle to be in the correct position, the bearing cups have to be unscrewed from the BB shell by 2.5mm each. If this is your case, then I think Hope make suitable spacers to fit between the cups and the shell. See
http://www.hopetech.com/webtop/modul...structions.pdf
and
http://www.chainreactioncycles.com/M...?ModelID=36416