Safer location?

Right now my 4 year old is FF in a radian, in the middle position in the back seat of my 99 suburban. His younger brother is RF behind the driver in a TF.
The second row seating (only the front and second row in my truck) has a 60/40 split. I'm finding the seat is being made to seem uneven, the cushion behind the passenger from having the FF seat pulled so tight.

My understanding is that when there are 2 kids in the back, the "least protected" one, which in my case is the FF seat, should be in the center. Is he any more unsafe if I put him FF in the radian behind the passenger seat? I could either leave my TF RF behind the driver, or move him into the center, the TF seems tighter without having to lean into it as much as the radian..........

Or do I just leave it as is?

The twist is that I have a 9.5 year old who sometimes, not too often though, sits in the back too (never in the front). There are headrests on both outboard positions in the back seat, but not in the middle. I had thought it was dangerous for him to sit in a seat without a headrest?

Any thoughts? I have the seats out right now....wanted to vacuum crumbs and make sure the harnasses were the right heights and stuff, so will wait to hear before putting them back in.

I'm not exactly sure what you mean about the un-even-ness. Is the Radian tipping sideways? How much? A little tipping would be ok, but it's subjective. Or is it turning a bit towards outboard? A picture would be ideal.

The middle position is statistically safer than outboard (can't remember by how much). So given equally solid installs outboard and center, he is statistically better off in the center. I would NOT put the older child in the center without a headrest (and what about the seatbelt, is it lap only in the center?) so if you move the Radian you would need to make the TF sit in the center, at least those times you have the older child. I would move the TF if you move the Radian, because 1) you would have at least 1 child in the safer spot, 2) you would have headrests for the older child, 3) the kids could interact better and 4) I seem to remember reading that having another restraint in the next seating position slightly improves performance, supposedly because it reduces motion in the restraints as they interfere with tipping/twisting etc by leaving less room?