All good advice senor crux,
re groundsheets, I tend to use plastic cut to the tent floor shape, and as said, if it extends far past your tent floor, it will collect rain, but also can easily be folded under, downward toward ground a bit to not stick out. I have a plastic ground sheet from an older tent that i use with my 2p tent the few times I use it, and just fold the little bit extra under with no problem.
never get around to cutting it down in case I lend the old tent to someone.