I've never heard of that brand. Guess I'll have to tak e ride today. Not that I need any more stands. That sounds ungodly cheap being as it comes with a harness--or is it just a belt? I would imagine the harness is generic and a pain to put on, but they cover their ass with it. Even so, a PITA harness is better than not using one.
Best advice here is to use it every time your feet leave the ground. Or get a better one. It's cheap life insurance.
As for platform size, I'm not a big guy, and never had the need of a large one. I've succumbed to the idea that a smaller platform makes me stay still longer, and I ain't up a tree to go dancing around anyway. My smallest stand has an 18x24" platform and sometimes I think that's too big---but not too often.