Still waiting to hear back from my buddy. Have you considered going with a pre-fab line like these Copper/Nickel 3/16" x 16" w/3/8x24 fittings??? Yeah, there an inch longer than your 15" length, but perhaps some slightly different bending would take up that extra length and make these work for you?

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)