True hypertufa would be too "soft" to stand up for a lot of traffic. When I make pavers I use a mix of 2 parts sand to 1 part cement. I also build them in two layers with a layer of chicken wire in the middle for extra strenght. Here is a picture of the leaf casting pavers I make -

Thanks. I was afraid that was the answer!

They should last through the cold winters okay, but I agree about the hypertuffa probably not standing up to foot traffic over the long run.

I just came across this site while looking for something else. It may have the answers you want.

Here is a link that might be useful: Stepping stones

Thanks, Pashta. I notice on that site that none of the stepping-stone links use perlite or vermicullite. Is it these ingredients that make "regular" hypertufa more prone to crumbling under foot traffic?

I am not an expert on Hypertufa, but I think you are probably right. I would imagine that both perlite and vermicullite would make it more delicate and subject to crumbling under pressure.