Time for a little Christmas computer modding.
After trying everything I could to get the Aquacomputer reservoir in the case, even accepting the fact that I'd have to twist and turn the case on it's side every time I needed to fully fill the reservoir, I finally decided that while the Aquacomputer reservoir is a work of art and the highest quality in craftmanship, it just isn't going to work for this build.
So, I will be switching from a single Aquacomputer D5 USB controlled pump and the Aquacomputer 880mL reservoir to using a PAIR of Auacomputer D5 USB contolled pumps, an EK-D5 Dual Top with a 60mm x 200mm (565mL) tube reservoir attached.
The up side of this will be a much cleaner installation look, the reservoir will be in the vertical position so it will be infinitely easier to fill, redundancy and added pressure with 2 pumps instead of one, and best of all, I can mount a 60mm thick RX360 radiator in the bottom with "push/pull" fans for added cooling over the 240 radiator that I would have had to use if I tried to shoehorn in the Aquacomputer reservoir.
While the 60mm diameter reservoir WILL fit in with about 1mm of room to spare between the 5.25" drive bay bottom and the 2 GTX 780 Classified video cards, that is just a little too close for me. Any sort of vibration or miscalculation on drilling a hole, and I will quickly start vibrating and close that 0.5mm gap and cause the case to rattle. So to avoid this, I have started to mark up and disassmble the case so I can Dremel out about 5-8mm of material from the bottom plate on the 5.25" drive bay and put the reservoir and pump tops about 3-4mm away from video cards and from the metal of the drive bay. This will allow a very nice view of the reservoir and still have plenty of clearance.
I also found some foam that I had laying around that I most likely will try using as a sound absorbing encasement for the flow meter. Nothing special, hopefully it will work. The price was right ... FREE.