Q about European seatbelt routing in a RF CoCo

[Snow mom]

I just got a new Combi Coccoro for traveling with DD. The manual states that RF you should place the shoulder belt behind the seat (this is called European style, right?) I was wondering though about having the shoulder belt behind the seat with locking seatbelts. I'm imagining the seat rebounding toward the back seat in a crash and the seat belt tightening and then DD hanging there with her seat flipped upward. Am I being crazy? Can someone explain the physics of this to me? My seatbelts only lock if you pull them out all the way so there's some chance I could get the seat installed without them locking as long as I'm careful to not pull the belt out too far.

[Joolsplus2]

Evidently the danger from overrotation (dumping back and down during the first part of the crash) is worse than the danger from rebounding (the bouncing back part that happens in most seats), and seats have been performing very well in Europe (and maybe Japan...Combi is a Japanese brand, but I don't try to decipher .jp websites very often!). It just adds an extra element of safety from the seat dumping back far and the head hitting the front seatbacks during the most severe portion of the crash.

[Snow mom]

Thanks, Julie. That makes sense. Since the CoCo can't be tethered RF, do you think the seat belt install is a bit safer than using latch where you don't have any additional reduction in movement of the seat?