I remember reading somewhere that growing in a bush shape is better for colder zones rather than tree shape. Does anyone in zone 7 or below have any success with trees instead of bushes?

We live in zone 7. One of my friends has a large Texas Everbearing, trained as a single trunk tree, that never dies back. The base of that trunk is probably 8-10 inches in diameter. He bought the house with the tree already established, so we don't know its history. My guess is that it was planted during a run of 5-6 years here with exceptionally mild winters. Then once it was well established the normal weather does not bother it.

Also, there is one old fig tree in town, with yellow figs, that is tree form. I plan to go inspect it soon for freeze damage since this year was so cold (low of 4F). I suspect that many varieties gain significantly in cold hardiness as they get older, thus allowing for the single trunk tree form.

Hi,
I'm a sevener as well.
I normally keep my trees in bush - and I only have small cultivars - Strains known to stay under 2 meters of height .
Keeping them in a bush is handy when you want to propagate them or give them to friends/neighbors - and if the winter kills a stem, chances are another one keeps growing.
But for 4 years I have a "longue d'aout" that keeps growing on a single stem - she's like two pens in thickness .
For two years, I have a BT, growing on two stems - those two don't want to make suckers - perhaps this year who knows ...
I'm now training 3 trees to tree form - but I leave most of them bush style.
It only makes a difference when the winter is really hard like in 2012 here. But I lost trees and bushes of the same strain / 5 lost + my former "Sultane" - February 2013 was just too cold for in ground fig trees.

So my conclusion was : I need a better winter protection system ! and I need the keep the beasts small for easy winter protection .

I'm planning on planting a few varieties this spring, I'd rather train them in a single trunk form, maybe I'd be better off keeping a few stems and a few years down the road trim it down to one?