Nice pics! Be careful about screwing into your back plate for short reasons and for resale reasons.
 
Your pics have me reconsidering going backplate-less

Razgriz2006
Nice pics! Be careful about screwing into your back plate for short reasons and for resale reasons.
 
Your pics have me reconsidering going backplate-less

I wouldn't rip the backplate off just yet. I ordered a slim 80mm coolermaster fan. It's only $11. 15mm in height. It should arrive Wednesday.
 
I think I could mount it with the preexisting screw holes or 3d print some clips. Place it over the middle area where the gpu bracket hole is, it'll draw nice circulation across the back pcb of the card. If you take the backplate off, you definitely need some heatsinks and possibly active cooling or at least good case ventilation.  I'll report back. I think the slim fan will accommodate the esthetics of the backplate well, hopefully. lol
 

I love barrow fittings but I'd be uncomfortable to use a block which bends the PCB that much

Pennywise359
I love barrow fittings but I'd be uncomfortable to use a block which bends the PCB that much

Honestly, I'm not sure if that's due to the waterblock or not. My brother and I were looking at it and we couldn't tell if it was like that before or not. I had heatsinks sitting on the backplate before I did the waterblock and I noticed afterwards that there were some sag. The pci-e slot is slightly curved as a result too.  :(

Pennywise359
I love barrow fittings but I'd be uncomfortable to use a block which bends the PCB that much

Actually after looking at it a bit more, that screw is not attached to the back plate nor the waterblock. I'll see if i can loosen it over the weekend. I think it's actually what's effecting PWR5 temp difference. 

 

 
Temps dropped a good amount. I moved the fan around and the best placement was over the gpu bracket hole in the back plate. You could feel it sucking air on the edges underneath the gpu bracket.  I'm going to order a Noctua NF-A9x14 HS-PWM 92mm fan since it looks like it'll fit fine there. It's 1mm slimmer too

Optimus water block
 
Spent four hours last night playing Red Dead Redemption 2, 4k, most settings Ultra.
3090 FTW3 +300mem, +150 clock
Ryzen 5900x, PBO off, no overclock

HWINFO averages over that four hour period...

Memory Junction - 50
GPU1 - 34
GPU2 - 42

PWR1 - 42
PWR2 - 42
PWR3 - 42
PWR4 - 46
PWR5 - 42

MEM1 - 45
MEM2 - 42
MEM3 - 40

buttabean



 

 
Temps dropped a good amount. I moved the fan around and the best placement was over the gpu bracket hole in the back plate. You could feel it sucking air on the edges underneath the gpu bracket.  I'm going to order a Noctua NF-A9x14 HS-PWM 92mm fan since it looks like it'll fit fine there. It's 1mm slimmer too

 
I'm using this bracket with x2 Arctic P12 in same box above the card.
 
No links allowed....good. Look for " Fan Mount Rack PCI Slot Bracket for Video Card " got it from amazon

Realize we are not directly comparable because full coverage block vs Hybrid Kingpin, but, figured I'd drop this for temp comparisons...
 
You can probably drop temps on your VRMs by doing some pads on the backside of them... you would also drop further with some heatsinks on the backplate:
 

 
It's interesting that the PWR/VRM temps are so different between the two cards in general, PWR4 is the warmest on the 3090 FTW3 types, whereas on the Kingpin it's PWR3.

Any block that reuses that stock backplate isn't doing the card a lot of justice imo. Especially with a 3090.