I've been using some older duofold tees underneath my jersey... they seem to do the job.. I bought them about 5 years ago for hiking and only used them once or twice... even on semi warm winer days (mid 60's here in SoCal) I have been using the long sleeves without feeling too hot or sweaty... they wick pretty good... I'm not sure if they still make duofold, or if Coolmax has sorta taken over.. but Coolmax would be a good choice as well

Jeff