This simply means there is no room in the actual slot, nor are the placement points accessible beyond those. You cannot have 1 medium and 2 smalls in a single arm. It's either 4 smalls or 2 mediums or 1 large, but you can have as an example, 2UAC20 in his LT/RT, 4 (SMALL) X-Pulse in his right arm and two LBX5 (MEDIUM) in his left. He also has two medium hard-mounts in his LT/RT as well.
Confused a bit. Is this a system/design limitation in general or a choice for the fafy in particular? Given the choice, I would want the example here to have 2sxpl and lbx5 per arm for greater area coverage and redundancy.
Helpers (the things that call in weapons through code, placed in Max) have to be named a specific way IE [fafnirPod_smallSlot_A_RA]. So, to get the most weapons in each arm I had to get creative with placement, which also created an inherent and inadvertently aesthetic limitation in weapons placement.
There was physically no room to have one Large+ and two small or mediums in a single arm without geometric clipping/overlap or confusing overlap of helper names (since they have to be named/placed in a specific order to be called in correctly). Same with Mediums, where when placed vertically they fill the slot to the point where no small/large can fit. Due to the unmovable nature of the helpers once the model is exported they cannot be repositioned.
To get the most possible weapons loadouts within his pods, he can basically hold clusters of a specific size at any given time per-arm. This means that once you pick a small weapon initially, your only choice is to fill the rest of that arm with smalls (up to 4), when you pick a medium, his arm can only carry two mediums, and when you choose a large+ weapon, he can only carry one.
You can still spice this up by having say two mediums in one arm, and a large in the other, or two clusters of 4 smalls (8 total smalls for both arms). The variety to mix and match is still there, giving him a unique ability to bolster larger numbers of various weapon-types, though the larger the weapon, the less you can hold. If I didn't do it this way, and stayed within the confined helper placement of the Generipods (just made that up) then he wouldn't be able to hold nearly as many weapons configs, nor would it look like it aesthetically fills the space properly.
I hope that clarifies things a bit.