I would look at staged injection for concepts. The total CCs is the total of all 3 injectors for Req_fuel calculation. In-fact, staged is probably a more effective strategy anyway, running on the two smaller injectors until demand activates the 3rd. The physical layout of each injector versus cylinders would be important for specific concepts of n-squirts and timing, so please provide that info.
The confusion: The point is not what Speeduino
should do, but what it
does do, so users can work with it reliably. A good chart should be created for how Speeduino really works for squirts and sparks, as there is a lot of confusion when a 2-cylinder 'even-fire' setting functions as an odd-fire twin (180).

The parallel twin is the only true even-firing option (360). All others are odd, and so expected function is not as would be assumed.
IMO: While it doing as we expect is preferable; the functional effects of the code become much more important. IMO a current and accurate chart would go a long way to side-step frustrated users thinking and spreading that Speeduino is less-than, when they are simply confused what it actually does and when.