^Chris would no better than I.
 
Instead of going through the headache of building the servers, I ended up just buying several 1U Thinkmate units. Each 1U server sports 4x 1080ti cards. More expensive,  but far less of a headache. 
 
cheers.

Most of my cards in my "riser rigs" run between 60 C and 65 C currently, some of them in the 50s C, despite the 80-82F ambient temperature in the room they are in and most of them running at 60% fan OR LESS.
The exception is a MSI "Aero" Blower model 1070 ti, which runs insanely hot even at LOW power settings - needs 90% fan just to keep it at 69-70 at 104 watts (TDP for the thing is RATED to be 180 - I don't even want to THINK about trying to run it at that power level).
 
EVGA single-fan "short" cards cool better than THAT piece of junk (as do Gigabyte ITX models and the Zotac Mini models and even MSI's own single-fan shorty models).
 
USB-cable style Riser rigs tend to be less expensive than shoving rigs into cases on a per-GPU basis, but the tradeoff is the "open" design is a bit easier to mess up if you're not careful around them.
They also DON'T work well if you are doing work on them that requires a lot of communication between the CPU and the GPUs, like [link=mailto:Folding@Home]Folding@Home[/link] or a lot of rendering type work, the lack of PCI-E bandwidth limits them quite a bit in those cases.
 
 There ARE risers that will transmit 8 or 16 lanes of data, not just one - but those risers with their ribbon or multi-COAX cabling are an ACTIVE pain to work with, the cable lengths tend to be very short, and those type risers tend to be EXPEN$IVE.