Hi Condor,
I have a lot of experience with multiblades, in fact I make my owns, from three to five blades, and I mounted and fly others made in China with good results...so my thoughts:
First...
BIGGER IS BETTER...the 700's size fuselage wil fly better than others, EVEN WITHOUT STABILIZERS
You do not need at all 3 axis Gyro or any electronics help, BUT...if you want to use just for sure I will recommend the cheaper Align 3G, I mounted an t-Rex 250 with multiblade head ( my own) and liked the stability, Rex 250 are twitchy to fly even with stock head, I mounted two Bell UH-1's flybarless, in all the same stability, even with hard winds.
I recommend the 3G because work well and better...is really easy to setup, the built-in tail gyro work perfectly for scales.
Now...I can pass to you some tips to improve the stability and control without the 3G ( or similar) and after finish the setup you can use the Flybarless with low gain.
In the video links below a few examples of my helis with and without Stabilizers...
http://www.youtube.com/watch?v=52TvGcpOGWs This one has the 3G
http://www.youtube.com/watch?v=9jTMMNdS0Wo as well this one...
http://www.youtube.com/watch?v=Omb1akbkLJ0 and this...
http://www.youtube.com/watch?v=8FbIcTF438I THIS HAS NOT ANY KIND OF ELECTRONIC..
http://www.youtube.com/watch?v=VuSgWNJrnas IDEM IDEM...
http://www.youtube.com/watch?v=VuSgWNJrnas THIS WAS MY FIRST FIVE BLADES HEAD, WITH CUSTOM MADE WOODEN BLADES...
Best regards,
Manuel