CarlC,
You're right about the stainless. boy is that stuff hard to work with. On some aircraft thrust reversers Dee Howard uses flare fittings and stainless lines. Hard to believe in this day and age a major aircraft modification center would use flare fittings on a 3000 psi system, but they did. Cracks resulting in leaks are common with these lines. All the thrust reversers I have seen other than these used MS fittings and never leak, or crack.