Hmm... I'd give it a try if I planned to never take it on the highway.

I would want to add electric brakes. My main concern would be stopping it. I can tell a pretty big difference in stopping distance pulling 100 lb. 250 lb would be a stretch without some extra help.

The secondary concern would be the wind, especially from passing trucks. I can feel my little trailer moving around in strong winds and it's a bit unnerving. I can imagine that would move around quite a bit more.