I finished the Ann McCauley square the other day using 4.5mm needles. It is 13.5" tall and only 9.75" wide in its relaxed state. It is pretty stretchy, however, so should widen easily to 12" and hopefully that will shorten it as well.
On a 10 hour (return) car trip last week, I knit the background to the Susan Rainey square using 4.5mm needles. It came out pretty close to a 12" square. I knit the 'sweater' yesterday. To finish it nicely, I did the increasing and decreasing one stitch in from the edge so I could use the mattress stitch to attach the sleeves. it came out quite nicely, if I do say so myself. I haven't attached the sweater to the square yet.
I started the Dana Hurt square last night. When I finish it, I'll be half done.
While on my trip, I bought the Interveave Knits "Harmony Guide: Cables and Arans" and will be designing a couple more squares incorporating some of those stitch patterns. I also want to design a square using the pattern from the Must Have Cardigan.