I finally paddled the 11'2 and 12'6 back to back this morning and Id have to say that both these boards are super fun. Keep in mind I have only SUP'd 3 times now (I'm no pro) and I do not work for Starboard

Both these boards I found stable although the 12'6 felt easier and easier to balance on as I kept swapping back and forth from the 11'2. It did take abit to get it but once wired they are easy boards to paddle.
With only the middle fin in both boards still paddled fairly straight but heading into the wind required more changing sides. I was told that by putting in the side fins in this will help straighten up the board for just paddling on a nice flat day.
Paddling for the waves only needed a good couple of paddles on one side to catch them although the experienced SUPer need only one deep paddle on the 12'6 and could even get the 11'2 onto a wave with not much more effort than the 12'6 although for me it definately seemed easier getting the 12'6 onto a wave. In saying that after I got the hang of the 11'2 I was catching more waves.
There were just rolling tiny knee high waves with some crumbling ones sneaking through.
The experienced SUPer had both these boards dialed but obviously rode the 11'2 really well. Both glided well but the 12'6 definately had more glide.
I think that the 12'6 would eventually be too big for me and the 11'2 would be needed.
I still think that the 11'2 can be a board to learn on and will never be too big or even out grow it for the waves here in perth.
Also I found that a good paddle makes a MASSIVE difference in paddle power and even felt like the board performed better.
Worth spending the extra to get a carbon paddle

After the paddle this morning for me being 68kgs, a beginner and wanting to SUP during summer in small waves the 11'2 is by far the board for me.
Hope this helps others out there like me trying to decide which board would suit them.
Two thumbs up for both these boards