Medium term choices include:
scale factor: How big is a heightmap pixel relative to (e.g.) trees, or the camera viewpoint.
An I going to actually draw the torus, or am I going to cheat and just draw cpoies at the edge of the map.
I really like the idea of the torus, and hopefully the transform isn't that expensive (I think it might just be a matrix multiplication, but there's probably trig in there somewhere).
Anyway. Sleepy time, g'd night fair reader.