AMEN about SIP - If you would not "run" to your "second choice" then don't put them down. Know, however, that if you SIP their could be a chance that you would end up without a bid at all.
ALSO, I, more then likely, would not tell the chapter that you are not interested in a bid from them, BUT on the other hand I WOULD TELL AQUARIUS that you ARE TOTALLY INTERESTED IN THEM. (not crazy interested but interested)
If you are invited to a sororities pref party you are somewhere on their bid list. You could be the last person on the second list, but you are there none the less. So, whether you are nice or not so nice to your second choice you are on their bid list somewhere.
ALSO (and this happens to every sorority every now and then) the worst thing you could do to a sorority is put them on your bid card then when they offer you a bid you decline. Because, when you write Aquarius 1st then Libra 2nd that means you would accept a bid from either sorority in that order of preference. So, I would rather not see the pnm on our bids matched list and know they SIP'd then to see them on our list and them not "run."
THAT IS MY TWO CENTS - oh yea have fun