I didn't had such problems. Temps are same as reviews shows and on Air and on Liquid.
But Immediately after Installed GPU I put styrofoam to hold GPU. I didn't even allow to GPU start to sag little by little.
Iphone put on backplate of GPU say that she is now in perfectly flat position. He have some measure for level inside and it's green 0 degree angle.
But I desperately search for ASUS TUF-ROG Universal GPU bracket available in ASUS X299 TUF Mark 1, Zenith Extreme and Rampage VI Extreme.
Some stores even wait to boards show on RMA to take him, but who knows how long I will wait and it's terrible because only Japan store offer TUF VGA Holder.
That's only small Holder and almost not visible.
It's terrible behavior of ASUS who not care about customers who need small parts they produced.
Once morning was cold and I saw Core temps on 25C and when I run Firestrike Xtreme Poseidon temp was 49C.
But mostly is 53-55C. I can say I'm satisfied enough to stay on this cooler and not to throw money for full cover block.
Instead of that I will buy one Black Ice Nemesis GTS 360 radiator.
EK, Bitspower, Phanteks waterblocks for ASUS GTX1080Ti Strix are compatible with ASUS Poseidon.
And that was very smart decision because PCB on Strix is enough for any kind of overclocking.