I don't think so? The first problem is the buckle receivers come up too high out of the seats, that's managed by the Tobi, but the only way to safely fit a high backed booster is to twist or wrap the fabric so the buckle receiver sits flush with the seat fabric, but when you go to plug the buckle in it falls back down and disapears!
The second problem is that there is a LOT of give in the seats so the up to four years old car seats are swinging left to right and to a lesser degree front to back.
What I really need is isofix! But I haven't seen anyone achieve this on a bongo

Alternatively a buckle receiver on a stick instead of webbing so it doesn't disapear, but then we're into new belts too I suspect
Thanks for the suggestion though!