2003 Ford Focus (four door sedan)
Rear-facing Cosco Scenera (passenger side seatbelt)
Fisher Price Safe Voyage booster, an inch wider than narrowest setting (center seatbelt)
Forward-facing Sunshine Kids Radian (driver side seatbelt)
Even though, looking from the front view, it appears that the FPSV booster is too wide, and is covering the outboard female buckle stalks, the design of that booster makes it all work. The way the seat is shaped, curving forward by the buckle stalks, near the back, with armrests set slightly forward, makes accessing the buckles do-able, and eliminates my worry of the booster accidentally releasing the driver side outboard and center buckle. We tried several other boosters in this spot (Evenflo Big Kid, Combi Kobuk, Graco TurboBooster), and none worked; they all pressed on the seatbelt buckles for the driver side outboard spot, and the center buckle.
It would probably work easiest to put a harnessed seat in the center, but I'm trying to keep my boostered child in the center if at all possible.
The RF Scenera could also be installed with LATCH, which I would actually be more comfy with, just so I wouldn't have to worry about accidentally unbuckling it when messing with the booster in the middle.
The FF Radian could technically be installed using LATCH, as well, and I'd be more comfy with that for the reason stated above, but in my vehicle, the child who would be using this seat is over the LATCH weight limit, so it has to be installed with the seatbelt. Still, because of how the booster is curved, I'm not concerned it will accidentally release the outboard buckle.