Im not 100% sure but dont you need to have at least .5 deg of angle from any joint? Otherwise the cups or needles get wore bad in 1 spot or the grease dosent get pushed around in them. I remember setting mine up on my truck when I swapped it. Was a pain to measure 20 times then do all the math and adjust the crossmember to get the height jusssttttt so.
I know that you need to make sure that the universals are "loaded up" so that they stay in business. All three of the universals in my driveline are at some angle either horizontally (the 2nd and 3rd universals) or vertically (the 1st universal). None of them are in-line, and the net angle is zero (or as close as possible to it) to prevent vibration. Of course the only way I'll know for sure how it all feels is to drive the truck, but that's a ways off yet.
Brian
'51 Chevy 3604 Project '28 Chevy LO basket case '83 GMC Sierra 4x4
