cmon, my father always raised me to be practical application over theoretical ideal. it's something i've been trying to get into you for ever. i love optimization but there are limits.
the only computer modeling even $20k headers get is diameter and length based modeling. and i DO flow modelling, i know how to translate from theoretical to actual application. the flow from the combustion chamber and valve end is so chaotic, that you can't accurately model its exact effects. the best you can do is take normalized flow and temperature data, and be close enough. and you don't need anything more than diameter and length to do that. sure bends matter, but on the exhaust, even ricardo wave doesn't model what radial alignment the 120 deg bend has vs the next 45 deg bend, which incidentally does do for the intake.
FWIW, in a subaru upturned UP/header situation i think the bellows joints are weak spots and double slips should be used there instead. but then you can't run super high PR on the compressor, blah blah.
jesse, sorry, your mom took all my wood last night.