Issue resolved. The "trick" was to push to the left (when looking at the car from behind), real hard.

I have a V50, made for Hungary in 2009, and this Christmas is the first time I'm trying to transport a long(ish) object in it -- a gift for my father. I've been trying to fit it in by folding the 40% part of the rear seat, but the storage cassette for the safety net is stopping me. I can't remove th...