luke: imho your D5 don't have as much head pressure as DDCs to handle as good much resistive blocks in single loop, so while it's true that in parallel connection each from your 3 gpus will get 1/3 of overall flow it will get compensated partially by more overall flow because of dropped restriction in gpu full cover loop part, and temps of gpu blocks are not that much dependent on flow. Well, you can always experiment, and if you get better temps for cpu & gpu in serial, so be it. But why not try parallel connection aswell, especially if it has worked better for some?