Is this a live steel (i.e. sharp) sword or a blunt item?
I've used the fiberglass stick for fencing targets to practice point control, but not for chopping/slashing sword work. One idea that pops into my head is a heftier target made with a 4x4 pressure-treated lumber post (tough and quite heavy), with 2x4 supports at the base extending outwards like an Brigid's cross. If you're using a blunt practice sword, pad the top with heavy carpet and rope wrapping. If sharp and you want to be cutting through something, I'm not too sure. Only targets I have seen for live steel are rolled tatami, watermelons or various meat cuts.