Okay, perhaps it's because it's super late and that **** Daylight Savings is affecting my brain - but man I'm having trouble parsing the Retrofitted hanger bay.
Lets assume we're building off a VX-100 freighter and we're trying to accommodate an X-Wing (for narrative purposes, we'll put it where the Phantom would dock). The text says that maximum silhouette of 2 smaller than the carrier. The VX-100 is a silhouette 5 ship, an X-Wing is a 3, so it should work right? Okay, that bit is easy.
The text goes on to say Sil 5 vehicles can carry a total silhouette of 5 - so my 3 Sil X-Wing and a 2 sil speeder bike should fit. (We'll stick it in the cargo bay somewhere). Okay, so far so good.
Then there's the mod - additional +1 maximum silhouette capacity, and you can do it 5 times. So assuming the awesome engineer makes all the rolls, the VX-1`00 now can hold up to 10 silhouettes worth of vehicles. One X-wing, three sil 2 speeder bikes and a Sil 1 Imperial Sky Swooper. This of course is putting aside that we've just invented TARDIS technology - strictly RAW, that's how the pieces mechanically fit together. But of course we're still restricted by the 3 max cap - no fitting a small-ish Star Destroyer in the Ghost's dock.
Okay, having typed all that out, my head is wrapped around this I think. But screw it, I've just spent all this time typing, so I'll hit submit so you wonderful people can tell me how smart and right I am.