The stock bracket thing that holds the bottom of the back panel onto the case is needlessly bulky, which made it impossible to route all the cables for my build.

To be fair to Phanteks, this case does predate HDMI 2.1, whose cables seem to all either be phat or fiber optic (and thus can't be bent too much).

I threw together this part which accomplishes the same thing, but leaves as much space as possible for routing cables. It reuses all the screws and nubs from the original molded part, and doesn't seem to compromise on stability

Print instructions

PETG, ABS, or PolyCarbonate are recommended. PLA is probably fine, if the amount of cables you're routing don't require pressing the panel hard into the case to affix it.

In other words, avoid PLA if the little nubs are going to have to hold back against some amount of pressure from routed cables.