Hmm.. If only two feet, probably just feel it out. Don't put it up any at first, and if you are struggling, then put it up a hole. If that's still ehh, then put it up a second hole, and figure out what felt best. (: I normally keep mine at a medium length and shorten if I have anything set up that's over 3 foot.
I have three stirrup lengths I ride at. My flatting length, my in-between length for a combination of flatting and smaller jumps which is one hold shorter than my flatting, then my jumping length which is one more hole shorter.
Unless you're riding really long if you're new to jumping I wouldn't raise them at all to start with for a 2ft jump - you don't want to getting into an exaggerated forward position for this height - just makes it easier to get catapulted off if you don't have a really firm seat
Maybe post a pic of your normal length?