It is slow. This ran on my Windows box for much of an afternoon. Below, I present a solution with using a coarse mesh. Here are some notes on the solution.
I noted is that the physical size is quite large. You can run into numerical issues when using large values. I choose to scale it by a factor of .001. That implies that material constants/loads would also have to scale appropriately.
The healer analyze option showed that two curves in the sheet had topology problems. I used healer autoheal volume 1 to fix those problems.
Working with the complex spline surface is slow in all operations. I will research if there is anything we can do on our side to improve the performance.
Thanks,
Karl
open "~/Downloads/topography.cub5"
body all scale .001
healer autoheal volume 1
create surface vertex 4 3 2 1
body 2 move z -400
create volume loft surface 1 2
del body 1 2
vol 3 scheme map
mesh vol 3
color curve all black