New plan: Got myself a Mars Computing MCMPro (basically the MC-400 w/o LED fans), which not only fits perfectly inside a Kallax shelf, but also does allow for
front / back / side cooling. Yes, its a bad bad MFF case with 24ish L, but there really arent much good options for smallish PC cases that both fit into a Kallax shelf AND offer adequate airflow.
Thats an issue with the SAMA IM01, which is optimized for top-bottom airflow, and would only work out somewhat if I was to flip it to its side and add some kind of feet / spacers; probably much worse.
This new case is, quality-wise, a very cheap cube case, with very basic features, but should do the job. Comes with 3 fans that I'm throwing out (apparently 2 pin), and even features a fancy TG side panel, which is ok I guess? But as I wont be using it anyway, its one issue less to figure out - the case is going to sit flush with its TG side to the left shelf wall anyway
Several advantages over the SAMA so far:
a) Two-chamber design - which leaves more space for eg. dropping a 2x or 3x HDD cage inside, although the PSU chamber already comes with a 2x 3.5" cage. Also, if the air cooling got annoying in terms of noise at some point, one could throw in a 120 mm or even cheap 240 mm AIO; the latter one being total overkill for the 12400, but maybe I want to upgrade at some point?
Also, this should help with eg. the Wifi issue. In the SAMA IM01 / Inter-Tech Pocket, I could not install the Wifi card without interfering with the GPU cooling. Here, I dont need a GPU, but even if I did, I could much easier setup / route Riser cables etc.
b) The airflow - mesh panel to the (PSU / HDD) side, back / front panel with albeit not huge but decent openings, which could be improved with a bit of strategically applied power-drilling; front allows for 2x 120, maybe even 2x 140, back allows for one 120
c) General fit in a kallax shelf - as mentioned before.
cu, w0lf.