I recently bought a Noise Tools 1U (very nice module, though the slew range is a bit limited) . One thing that I found super annoying when installing it is that the power connector is on the top of the PCB and oriented in such a way that the cable goes up and thus bumps against the rails right away. It took me some time to be able to fit the thing nicely, I didn’t have that issue with any other module (1U or 3U).
It would be a good idea to check this for all modules, 1U is a bit cramped so this can easily become a problem…