my take on the issue. the program already put aside a whole day of cases, clinic, and what not to put on the show. now you want to tie someone up just to look interested? if i were that person, i would probably be really annoyed unless the applicant had some very valid issues that didn't arise during the interview. i don't believe that there is anything that can't be answered over the phone/e-mail.
that being said, there were some programs (ie. mayo) that specifically told me my position would go higher on the rank list if i came up and spent a day with them in the clinic or the OR. so, if i had really wanted to go to mayo, i would have taken them up on the offer.
bottom line is that you are walking on very thin ice with these "second looks". my feeling is that you will more than likely do yourself more harm than good. if you really have thoughtful questions, take some time and compose an e-mail to them.
hope that helps.