Ok, my view on this topic: I agree most with Brad on the brake line issue. I too, have replaced many brake lines and cylinders without trouble, and have made many double flares on steel lines. My experience with double flares is that the first dozen or so should be for practice, then go cautiously with some for 'real.' Also, with double flares, if you get a bad one, you have to cut off about an inch of line before trying another- the steel line work-hardens, and if you just cut off the flare, the hardened line won't flare properly- although it might look alright. I didn't see any reference to the flare angle in this discussion, but the wrong tool will give the wrong angle, and after tightening the new flare, the flare seat will be distorted and unusable for anything.
In my opinion...
Harvester