Rick,

 

I don't know much about the double wall flare, but I bought a Parker Hannifin flaring tool and it did a flawless job of flaring the brake lines.  It seemed like a good compromise between the really inexpensive tools and the $500+ tools.

 

 

 

 

 

 

 

 

I think improper technique and incorrectly fitting and securing the tubing in the aircraft are more likely causes of brake line failures.

 

I also used the fitting seals on my flared tubing connections.

 

 

 

Mike