To the hand:
When antes kick in it's better to calculate in "true BB" - there is a very good post from bond regarding this issue - you can find it here:
http://forumserver.twoplustwo.com/showfl...part=1&vc=1
So usually (if the table is not very loose) it should be alright to push from the CO with 12BB with JTs as you will be down to about 7 "true BBs).