if you want to eliminate or minimize distortion,
add the braze-ons to the tubes, and then add
the tubes into your fixture. if the frame is brazed
up and then you heat small areas helter-skelter
with varying sizes of metal to be added, some bulbous,
others assymetric, it is a recipe for trouble, especially
if you cannot assure yourself that the frame was built
stress free to begin with. that's the cliff's notes reason
for doing the braze-ons first.