I've just noticed that you have attached the rear of harnesses to the isofix points. I've got mine fixed to the seat belt clip points. I might try that?
These cages were originally manufactured by Caged for the Motorsport Vision 182's at Oulton Park. The design is very clever as it bolts into existing points and can be removed without trace.
Cages can be bolted or welded - welding being the better (and more disruptive) option. Plenty of competition cars have bolted in cages, although admittedly the higher level you look, the more likely to have a weld in cage you are...
Hiya Matt i put them to the isofix points because tthey tighten up the harness nicely and are more central to the seats.
The reason for cage is both cosmetic and functional it ain't in your face like a show cage and does a job aswell. Plus i can take it out and no one would know any different.