I ordered a book via FIFO (i.e., not a WL book). That copy turned out to be the wrong book. I ordered a second copy, also not WL, via FIFO. That request was accepted and marked mailed. In the meantime, there is now a WL for this title. If the current copy doesn't make it to me or is RWAP for some reason, do I become #1 on the WL, since I ordered my copies before there was even a WL for this title?

Obviously I'm hoping that the current copy arrives in good condition, but was wondering how the system deals with WL placement in this scenario.

I think you should add it to your wish list now if you anticipate any problems than you will at least be high up on the list.

But that would put me at the end of the line, whereas I'm not sure where I'd end up if I let the system do its thing. 

Plus my WL is full. 

I'm not sure what would happen, and I don't think it's in the help docs, your best bet is to use the Contact Us link to ask them ... maybe they can also put you on the wish list as of your date ordered, if that's not what will happen already.

I'm pretty sure you get put on the WL if there is a RWAP and there's no longer a copy of the book available to order; I seem to remember that happening to me once. But I think I was the only one on it, so I don't know if you automatically get bumped up to be first in the line. It certainly would be logical for that to happen.

Wish List Ordering goes strictly by Date Wished. If you RWAP a book that was on your Wish List, you do go back on the Wish List in the same position that you would have been in before you ordered the book ... strictly by the Date Wished. You are not put back onto any Wish List at a specific position. If you have the earliest Date Wished, then you are #1 on the list, etc.

I don't know if the PBS considers "Date Ordered" on a non-WL book that then becomes a WL book to be a "Date Wished". It would actually be logical if they didn't, as they are 2 different things. Or maybe they already accounted for it this situation in their programming. But you need to ask them that, I think.

In the time you ordered this book and it's on it's way and just became a WL book could the Wishlist have gotten that big?

It's a WL of 3 as of this posting.

I don't know about where it would put you in line, but I think it would go by request date and put you first, unless some of those wishers had had the book on WL old until now. 

As for your WL being full, I believe you would be allowed a temporary overage.  I know they do this when a WL books goes lost or is RWP and in the meantime you have replaced that spot with another book.  That's why you might come across someone with 201, 203 or similar on their WL.  (or 301, 302 etc.., for gold key members). 

Yes, if it goes lost or is RWAP I would have a WL of 201. I've had that happen a few times. I'm hoping it arrives OK but was marked mailed 1/21 and has yet to be scanned. Sender printed and marked mailed immediately after printing so I'm hoping it's just a delay between being marked mailed and actually being mailed.