Good advice, so I should book my 1 night harbour view first, then a back up 5 night non-harbour view room in case the next 4 bookings don't work out?
Do you think I'll be able to do all of that straight away, or might I miss the back up availability and have to wait for the half hour to roll around?
So this may sound bananas but this is what I did...in a nutshell I did the reservations concurrently.
First, I set up two different accounts with TDR so that I could be logged into both at the same time, in two different browsers, Chrome and IE. (I'm not sure this is necessary but abundance of caution, you know...). When my laptop clicked from 8:59 to 9pm, I immediately clicked my harbour view bookmark on Chrome then went over to IE and clicked on the 3 night stay piazza view bookmark - it takes a few seconds for the rooms to display so you have plenty of time for this (and I found Chrome to be faster than IE so I used Chrome for the more important reservation). Then I went back to Chrome, put the harbour view room in my cart, clicked back over to IE and put the piazza view room for three nights in that cart, then went back to Chrome to finish that transaction.
Once the room is in your cart you're pretty much golden barring some sort of technical snafu, so you can afford to be very careful inputting your card info and whatnot. There's no time limit to complete the transaction that I ever ran across though it's probably like 25 -30 minutes since that would jibe with the release of additional rooms at that time. In any case, you have plenty of time to complete the main reservation before going back to do the backup one.
You could probably get away with doing the main reservation first then going back and doing the backup rather than doing them at the same time, but that has some risk in it. It was pretty easy to do both at the same time- but I highly recommend practicing it. You need to be fast and accurate with your mouse.
Writing this all down makes me realize just how ridiculous this whole process is, but I viewed it as a challenge and was pretty happy on the third night when I managed to book the third of the three one-night reservations. Made all of the preparation worth it, maybe. Honestly I would have been happy with a Venice side room but my wife was pretty excited about the idea of looking down on the harbour and kept playing the we're-only-doing-this-once card.
Let me know if there's anything else I can do to help! And please notice I've added u's to "harbor" just for you, Meryll83!