I was finally able to model the new hotend holder, which uses aluminium plates for its construction. No longer do I have to worry about the holder unintentionally melting, sagging due to the weight, or blocking the view when inserting the heatsinks into the couplers.

This was one of those things that is kind of hard to model because when there's nothing but an empty canvas, it feels like every plate depends on every other plate, thus a cyclic reference (aka catch22 / chicken and egg problem). 

I initially was planning on a jaws-based solution similar to the redesigned holder for R2, but had concerns with grip so I just went with grub screws. This design allows all 8 heatsinks to get a grubscrew.