"...so far it seems like the hardest MINI I've yet encountered to get car seats into..."
Paul, if you keep the clubdoor closed it should be just as easy
as with the three door, maybe even easier, since there is more room, door opening is the same.
I have no idea why anyone order the three seat backseat. There is only room for two, the back is just cluttered up with seatbelts and headrests.
What made you think it was a practical car?