I have a 1.4 5dr N-Tec and have just purchased a Mimsafe Variocage for my dog. This cage has tiedown straps but I cannot find any D rings or other tie points in the boot/when the rear seats are down. Would it be OK to tie the cage using the upper rear seatbelt attachment? One strap on either side of the cage, attached to the seatbelt attachment would hold the cage in place but I'm not sure if the sideways force would damage the seatbelt attachment.