Just to add my 2c. I double flared my S/S brake lines. I too heard that it couldn't be done; too hard, would crack. Then I read either here or on another forum that if you anneal the S/S it will double flare just fine. I tried it and it appears to have worked. I say appeared because other than a few trips to the house from the shop and back it has not been tested on the road. However so far I can find no leaks after bleeding and the afore mentioned trips. After annealing it double flared quite easily.

Jack.