I don't see the need for a hose barb to hard line adapter. In stock form the miata's hard lines just have a double flare on the end and the hose is pushed over that and clamped.
I'm using 5/16 Aluminium hard line. (from Summit) It's much easier to bend and flare.
Well dang...the low pressure hose goes over without too much trouble, but I can't get the high pressure hose over the flare on the 5/16 line for anything. I've tried spit, soap, and every bit of muscle my fingers can muster, and it just doesn't quite
stretch over it. Argh.
I'm going to go buy a pair of inverted flare to barb fittings tomorrow for the high pressure hard line. I won't bother for the low pressure side.
I was tight for clearance for the bulkhead fitting, -8 to -6 reducer, and a 90* ell (in either -8 or -6), so I ended up changing out the -8 bulkhead fittings for -6 bulkhead fittings. This made things simpler, and cheaper, too. Wish I could return the -8 bulkhead fittings that came with the tank.
Time for bed now, but I'll post some photos and more commentary tomorrow.