Car Seat Logic Puzzle

The advent of my third trimester has me contemplating logistics, especially those pertaining to car seats.

I need 5 seats in our suburban come April, 4 full forward facing seats and an infant seat. Our 50 pound 6 year old has frequent meltdowns in the car due to sensory and other challenges, so I must keep him in a five point harness. I can’t move the 5 year old into a booster without inciting more meltdowns since the 6 year old would remain in a car seat. The 6 year old cannot sit next to the infant. I would like the 3 and 6 year old in back with our carpool seat (not always in use) in between them and our infant and 5 year old in the middle.

I can get three in the middle easily, but then two kids have to climb over the back seat through the rear of the car, which is awkward and painful and not a very practical long term solution. I would like to keep one third of our middle bench row folded down so kids can get in and out of the car and I can help them buckle.

I have scoured car-seat.org and other car seat forums and my head hurts. There is anecdotal evidence of 3 Radians in a third row of a suburban, but no one has posted an actual picture of this set up in a Suburban. I cannot ascertain if a minivan third row is wider than that of a suburban since the wheel wells take up so much room, though I will try to measure a neighbor’s minivan and compare this weekend. As much as I would rather not swallow a fortune worth of new car seats, I do have two forward facing ones that are about to expire anyway.

The Radians are 17″ wide and the Chevy website says there is only 49.4″ of hip room in the 3rd row, which would make it an inch and a half too narrow. Does anyone have any experience with 3 forward car seats in the back of a suburban?