Sorry about the delayed reply: we had a few days away, and we tend to leave the tech stuff at home.
I don't think this would work as the floor is for a ten foot Zodiac and your boat is a thirteen foot Humber. Nice sibs. I don't know why they went from sibs to ribs exclusivrly.
I have messed around with inflatables since the seventies and I really think you need a Humber floor in a Humber boat. I've found that length and width need to be exact, or you finish up with scuffed or nipped tubes, or, worst case, floor separation.
Hopefully someone on the forum will have an answer or even a floor for you. I'm sure it's the best bet.