Whatever solution you go for, get a dancer and/or a risk assessor to look it over before use.

You're better off using a professional stage as they will be insured. If you make your own and an accident occurs, you could be held liable for damages, which will certainly cost more than the hiring of a professional stage/floor would.

I've seen many a dance floor and a few dancers come to grief because a home made floor was badly supported, poorly laid and downright dangerously placed. Corners are the obvious place to look at for scuffs and bends but if the sides are not adequately nailed down every 8-10 inches, they can start to buckle or bow. Plywood can be quite flimsy and very flexible. The best thing to use would be industrial grade at more than 1/2 inch thick. You need to support the middle of the sheet as well as the edges. Ideally, there should be no more than 2 square feet unsupported across the body of the floor. On no account should you use hardboard other than as a topping over plywood. I've used a pretty good floor made with 8 industrial pallets over which had been carefully laid, rough side up, a hardboard 'veneer'. This served as a very good floor, as the rough side of the hardboard was less slippery than usual floors.

I've known floors to 'migrate' down hill during a dance because they had not been secured in place well enough, and I've seen them fly apart in the middle due to inadequate securing - cable ties are not enough!

Good luck!

LTS