I love your build (and am very jealous of your l5, they are hard to get these days ahah).
But instead of partially obstructing the front fans would there not be enough space to place the HDPlex GaN unit in the free volume between the CPU Cooler and the sidewall.
It wouldn't have to be directly above the cpu cooler, mabe more towards the Ram, or maybe closer to the GPU backplate?
Just a thought, though maybe you wouldn't have enough clearance for cables to plug into the hdplex anymore. i would love to see a testfit though. been wondering if this config was possible for a long time.