Regarding the screens. The Hasselblad acute matte screen was a design from Minolta where they used hexagonal cells sandwiched together. This meant no dead space and more transmitted light. There wasn't more contrast though it was brighter. I've tested some of these Minolta patent screens as they are sometimes referred to in my focus tests and think the High D screen now or the Bill Maxwell screens yield more accurate focusing. I found with the acute matte screens that you'd think you were in focus and then you'd move the knob and not be sure - it didn't just pop in to focus at one spot. I know these are 'legendary' in the Hasselblad lore, but I found them to not live up to the expectations other than brightness. Maxwell screens and High D screens were the only two screens at the top. Actually the ground glass screens have the most contrast of them all, but are not as bright and are dark in the corners. I've been meaning to experiment with a fresnel over the ground glass screens and have asked Steve Hopf to grind me a very thin borosilicate screen such that both the fresnel and screen could fit.
Overall the matte screens are better than the split prism screens for manual focusing.
I find that using the lupe finder the best for manual focusing, followed by the 45 degree prism.
Focus spot size setting in the options menu affects the size of the active area, not the location on the screen. I usually keep mine set to small.