If you look at the drawings for each type of flare, then there are two types of bubble flare - the modern DIN/ISO flare and the older Girling flare. Fortunately, as Trevor has said, they are pertty much interchangeable, particularly if you use a tubing line Cunifer, which seems slightly more maslleable than normal steel tubing.
And yes, you can get away with quitting a double flare half-way through.
"Pace" professional automotive engineers. I'm just saying what works!