That looks great Alistair! You probably found that the strings don't have to be particularly tight in order to hold the secondary stable, which is nice. I was surprised with how little tension they need. People often get the impression that it's pure tension that holds a wire spider in place, where in reality it's the geometry (at least when you make the geometry right!)
I see you used the same system of pivoting guitar machine heads as I made for mine. Have you adjusted it so the wires are squared yet or is this just a test? It can be a little tricky to adjust exactly but you only have to do it once
Cheers,
Rolf