The hutch you've shown looks like some that we used to have at the rescue.
The wire in the door isn't fox proof,and if its the same hutch, the wire sits inside a ridge, which means the buns can chew the wood from the other side, making it really unsafe. The ones we had were rubbish.
4ft or 5ft doubles are not really ideal for 2 buns, as you lose a good 12" of each floor from the hole and ramp set up, which means they don't have room to hop.
I'd aim for a good 6x2x2 with a good 6x4 or 6x6 run permanently attached.