Hi Brendan,

> Before I do this though, is there a way just to use the two perpendicular axis ('rails') to make
> a solid in one or a few passes?

I'm not sure if this is exactly what you're asking for, but it is possible to loft the long rails you have with each other rather than lofting the vertical stations.

That would be something like join the pieces together so you've got 4 long curves like this:



Then select those 4 long curves in order and run Construct > Loft, and enable the "Closed" option on it to make it a closed loft, that will give a result like this:




If you want to try Network to get more control over the roundness of the shape try doing it just as one big Network all at once rather than doing it only in small separate sections at a time.

- Michael