You can't really compensate for overexposing by reducing
development. Reducing developing time will reduce contrast.
It will also reduce overall density. So the negatives may be
easier to print but will need to be printed on more
contrasty paper than usual.
 For most film reducing development time by about 30% will
reduce contrast by about one paper grade and film speed by
not quite a stop.
 I would not reduce development time more than this.
 The speed setting will depend on how much infra-red light
there is. On average away from the equator, there is
considerably less in winter than in summer.
 However, since the amount of IR is hard to measure with a
normal exposure meter you must test. Bracket about one stop
more and one stop less than you think is correct. Even two
stops more and less may be helpful if yuo have no idea of
the amount of IR light. One test roll will let you know how
to expose for those particular conditions in the future.