I'm impulsive and having a really, really messed up phase so I thought to myself "Why the Hell not?" and put my Kraken G12 and Asetek 570LC (a 40mm thick 120mm AIO) on my Reference RX 5700. For your information, the bracket does fit but it's a bit tight. The screw holes for RX 5700 are essentially identical to R9 290/390 series, but the width of the hole is a bit smaller from what I gathered. The bracket fits but needs a bit of 'Convincing' to do so.
I also installed copper heatsinks onto all of the GDDR6 memory chips, and some small aluminium heatsinks on the VRM for the Core and Memory. I couldn't fit one on what I think is the SoC VRM, good thing it doesn't use a lot of power in my understanding.
In order to go over the pre-defined limit of 1850 MHz (which actually results in around 1750 under load on my card) I used this tool to create a Soft Power Play Table. To get the defaults I just use GPUz to dump the card's BIOS to a ROM file and load it into the tool, set the desired limits in the SPPT, apply, and restart.
Here's some pictures of my bodge-job with a hot-glue gun.
For your information, in case you are silly enough to use my ramblings as a 'guide' to do this (please don't) the lower heatsinks in the below photo are a little too close to the GPU package. I had to unmount them after screwing down the cooler (and then lifting it up a bit) and push them back a bit. The result is only about 60% of the GDDR6 chip has a heatsink on it, but the temperatures are pretty good and nothing throttles / errors so I assume it did a reasonable job of cooling them.
Also please note my case is Silverstone RL08 and the card is exposed to 2x 140mm High Pressure fans at all times, only 2-3 inches from its surface. This is pushing air through all the crevices and over all the heatsinks at all times. In a less ventilated case these heatsinks will likely not be sufficient on their own.
I am not using YouTube as I disagree with their policy and thus, I cannot use the service without accepting it. I also hate seeing everyone downvote my videos. As a result I share my videos to those interested in them, via my OneDrive. You can view the image directly from the OneDrive link or you may download the original File to view locally.
You can find it here.