This doesn't answer the question - it just reminded me of something.
Off on a bit of a tangent...
If you look REAL close in the fullsize version of my avatar, (below) you can just make out the carseat in the passenger seat.
YES - I took the child out BEFORE that pic was taken.
When my son and his mother went out wheeling a lot with me, I needed a better place to put the car seat.
So I made up some brackets that went between the seats on the flat area of the floor just behind the seats. The carseat hooked into the brackets more securely than it belted into the regular seat. We padded him up in his seat with some rolled towels so he didn't get bounced around so much.
It was almost like having him in his own little racing seat with 5 point harnesses.
It actually worked pretty well and I felt better about having him there than I did in the passenger seat especially with no doors.
Now this is from a time long ago, in a land far away and is probably not really legal for carseats today. But I just thought I would share.
Yes, we did have permission at that time to ride that particular set of powerlines. Also probably illegal / off-limits today. Due to people leaving trash and riding off the trails on to posted property.