I've got the same kit, bought a few months ago. The cloth-backed sheeting was quite badly warped, so bad that some of it had split.
I tried to remove the cloth by soaking, and it curled so badly that I ended up with a 25mm diameter tube. One side is effectively waterproofed by the glue used to attach the cloth, so the plain side expands, the cloth side doesn't. The parts will be used as templates to cut new sheeting.
If your sheeting is flat enough to use, make sure that you waterproof everything after assembly. I dread to think what would happen if it got damp after being built.