Back to the original post, can you mark more than one preferred loop?
I'm the OP, tmoo, and to tell you the truth I don't know if you can mark more than one but I don't think you need to. The last three trips I've always checked "100 Loop" and "Close to a Comfort Station". In those three trips, one time I got 100 loop, a second time I got 200 loop, and the third time I got 400 loop (I rode through 100 & 200 and there were no empties at the moment I checked in and 400 is the closest Premium to 100). So I don't think it gains you much even if you can because they will try to put you in the site level you paid for in or close to the loop requested. (I am assuming you didn't want a Preferred pet loop which the only choice is 300).
Other past trips when I requested 900 loop, the one time I didn't get it they put me as close to it as they could in the 1000 loop - which was fine because I wanted to be close to the Meadow Trading Post and pool anyway.
The one thing I will say if you are really HUNG up on getting a particular loop is if you don't get it when you check in, offer to wait if one is coming available. We like to check in early (before the official 1pm check-in time) and the Fort Cast Members need time to clean/prep sites people leave that day so sometimes they aren't even available for assignment until later in the afternoon. Of course, that's only if someone left in the loop you wanted and it has to wait for the prep. But we have done that too - I wanted 1500 in 2012 and got there a little early. But I waited and the CM said one would come available later that day and she assigned me to it - she just didn't tell me the number.
But she said she would text me and she did and I got the 1500 site number in the text and drove down right to it.
Remember it's a request, not a guarantee but the Fort CM's try to do what they can to meet visitors' requests. Sorry for being long-winded but to answer your question, I firmly believe double checking loop numbers doesn't help (if empties are available in both, how do they know what your first preference is?).
Bama Ed