So - what rear fitting setup is optimal for Sierra rear disk brakes with "angled" (or Talon) uprights ?
I thought about straight fittings, but maybe angled 45deg. or 90deg. fittings will suit better ?

My build is not at this stage at the moment ;)

Hi Lucas,
I would say it depends where are the brake line brackets located on your chassis. This will have direct influence on the angle the brake line arrive on your rear calliper with. The angle should be as natural as possible.
Straight fitting are very nice because they are very compact. Angled fittings, (45° and 90°) are not as compact because of the angled tube, so better chose them only if you can not fit a straight fitting.
We use a 45° fitting on drum brakes with "book" upright, because they allow to fit the brake line directly into the drum cylinder without using the piece of copper pipe as explained in the book.
Personally as I have "Talon" uprights (angled RU8) like yours, and drums, I have a straight fitting in the wheel cylinder.
For rear disk brakes with "Talon" uprights, I think a straight fitting should be OK. But of course, as I said above, it depends where your brake line comes from: the important thing is to have a natural angle between the hose and the fitting once the brake line fitted.
Hope this will help :)