I've taken my 55kg German Shepherd in my Leon a few times but he really hates it. I have to put the back seats down and then cover the whole car with sheets/dog blankets and make him wear his rain coat or it'll get fur everywhere (and he's white!) Whilst he's in there I also have him connected to the seatbelt via a dog harness as its a legal requirement to have your dog secured.
As I said he totally hates the Leon as its very uncompromising in its current state of tune!:blink: