When running SLI, especially with aftermarket coolers that are not of the blower design, the top card tends to run very hot, unless you have an ATX-E style motherboard with more x16 PCI-e slots so you can space the cards out further.
This means, that even using cards with great coolers, like the Asus Strix series, the cards hit thermal throttling, pretty much no matter what you do - The air between the cards simply will not move enough.
I have fought against that by adding fans on the side that with brute force pushes the air in between the cards ever since I first started using SLI in 2006.
In 2017(?), NZXT released an update to their solution on how to mount AIO coolers on graphics cards, the NZXT Kraken G12 (Update from the G10) with an improved mounting solution. I was gonna do this back then, but since lazy, I never bothered. Thanks to Sinful gifting me a gift card at a computer store, I went for it.
I was able to keep the backplate and the strengthening bracket.
Idle temp went down a few degrees in a cold system, and load temps went from 83c (Throttle max) to ~49-50c.
Since there is no residual heat in the case anymore, every component is now cooler, and I removed 3 case fans.
Only downside currently, is that I am using stock fans, both for the GPU bracket as well as the radiators, and the 92mm fans on the gpu brackets run at 100% all the time.
Yeah, there is no build log.
Here is the result on my Asus 980TI Strix cards: