Get the re inforced polystyrene for the storage box and it’ll be fine. I don’t even think you can put rear facing seats in the boot can you?xx
@Emily oh I didn't know about filler boxes! I'll have a look. Thank you!
@Kiera thank you! I didn't think so but the fitting manual said its fine which I thought was strange. And I wouldn't feel comfortable with it incase I had to get her out quickly so would have to be the middle seat if we can't sort out the compartment issue but I think the filler is a good shout
Check the vehicle manual. It will tell you what you can do. Depending on year it’s either you can put on top, extend leg to bottom of storage box or use a filler in storage then can put leg on top.