Smithie and i net on some land in the dales and each season we start with 4" 4z nylon nets but as the season progresses we move to 4¼ " 4z nylon then come Xmas time were using 4 1/2 spun poly double strand the reason being that the rabbits put on a hell of a coat which makes them seem larger than normal.
edited to add...i answerd this using my mob and rushed, i also accidently pressed a couple of you guys names (so dont think im stalking you.lol)
i like to use 4" 4z at the begining of the season so i can catch both full grown and 3/4 grown rabbits but come october i change to 4 1/4 mes