Rambo-
Per my understanding, the only difference in the substitution cases was that INS has to refer to the original LC that was used. Getting the original copy of the LC shouldnt be that difficult at all for the INS, unless and until they follow a really primitive method!!!.
Yes there could be a delay (about 10-15 days, but not months to get the original LC).
Assuming the fact that the date (5/17) INS is processing, we havent seen any approvals. I hope people are updating the posts.
Guys, could we please update the post after you get the approval.
-Thanks.