Stainless is an extremely hard material, requiring far more force than the "soft" steel lines available at parts stores.
This topic came up on a Corvette board a few days ago, everyone there (including some professionals) agreed that it requires a large amount of force to flare them properly.
That said, the "soft" steel lines are quite durable. Just give them a good clear coat after getting them to the correct shape and don't worry about it. If you really want stainless, they're available from the vendors.
PITA = pain in the ...
