I had two rear hubs done but none of the holes for the brake disc mounting screws were lined up and the hackjob of drilling and countersinking new holes in the brake disc was something I didnt like.

The mounting holes in the hub are oriented 180 degrees apart from what I can tell. The holes in the 914-6 brake disc are more like 175/185 degrees apart.

Is there any particular way that is better than the others for orientation of the hub vs the brake disc?

I want to be able to give as clear instructions as possible to the machine shop.

Take him a rotor and hub. The 914 and 914-6 use a different hole pattern ( same as 911) for the rotor to hub screws. Either redrill the hub to match the rotor or rotor to match the hub. Also be aware that the 914-6 rotor is 4mm larger in diameter. If you are using 914 calipers they will rib. Either need to grind out caliper metal or turn down the rotor to fit.
One way is not better than the other. Or you can forget the screws as the rotor is going nowhere once the wheel is on.
Bruce

many new cars don't have these screws, the rotor is just held in place by the wheel and caliper.

Yes, not required. When I did my rear conversion I asked eric specifically about this. I have run many years without the locating screws.
Carlos

No screw required.
Only you will know.

If you don't put the screws, any of the disks could move on assembly making that wheel out of balance.
I decided to source original parts instead of "modified" ones.
Mike

no it won't. installing the wheel with 4 (or 5) lug nuts/bolts will properly seat the rotor

The disk will be held in place by the sandwich of wheel and drive. Trust your life to that, factory didn't.
Early cars have no centering rings.
Building a car for the "look" that is fine but these cars were meant to be driven, compromising that is unsafe especially for the next guy you sell it to.
Mike

I would also recommend getting centering rings from Tangerine Racing if you are going to run what you have.

Pretty sure the factory only had screws so they could use lug bolts. Studs render the screws unnecessary (as on almost all modern cars).

"Modern cars"

Move where? What will two little screws do that five large studs torqued down to 90 ft lbs. won't?

I had the same issue using 911 rotors with redrilled 914 hubs. Holes in the wrong location.

Ended up using the holes in the rotors to drill and tap the hubs for the new hole locations. Problem solved.

"On assembly" you trust some mook at Discount Tire Express to make sure your disks are centered ?
You might take the time to do it right.
Mike

I usually do it on the lift at our Porsche shop.

Not everybody has a "Porsche Shop"

I don't think the brake rotor could get out of balance if the screw isn't in place during wheel changing by itself.

What could happen is when servicing the wheel, the rotor becomes dislodged, and dirt or debris gets between the hub and the rotor, causing the rotor not to seat correctly and resulting in brake judder.

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"On assembly" you trust some mook at Discount Tire Express to make sure your disks are centered ?
You might take the time to do it right.
Mike
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The discs center on the back side to the hub. Screws have no effect on centering, safety, or function.
Your on the wrong track on this one Mike.

The screws are more of a ease of assembly deal.
Likely on the factory floor the rotors were installed and it was several workers down the line before calipers went on. The factory just wanted a quick way of holding them in place so they wouldn't fall off and on the floor.

Taking the screws off can be a pain if they seize on.

It all depends on how loose the rotor fits over the studs. If you hold the rotor against the hub and can still move the rotor around, you may have a centering problem. I saw this last year. The rotor actually hit the inside of the caliper it ran out of round so much. If there is no play, then you have no worry.

+1.
you must be thinking of hubcentric rims vs non-hubcentric rims....