I'll look into that machf.
I'm thinking about just making a 1 sided model and placing it high above the terrain. A 1 sided model isn't visible from below and casts shadows. You just move it around till it matches up with the terrain. That would give it hard shadows. I'll get back to this project when I get home.
I'd prefer to avoid using baked textures because they are blurry up close. And I like the texture layer system in Tresspasser anyway.
Edit: I'm gonna generate an image like this and turn it into a 1 sided model. Then place it above the level to generate shadows. I bet this is the best way. I'll generate one that matches the current lighting in the level. I hope this works.

Edit: I checked, I can move models around in GUIApp and see how the shadows cast onto the landscape. This will make it really easy to get the model lined up.
As you provably know TresEd doesn't render shadows on newer pc's. Technically TresEd can but I gotta disable my external gpu and use an internal one. In my case a Intel gpu. I would also assume an old external gpu would work. But I don't know how old it would have to be. Most people wouldn't care about this though. Its a directx driver issue I believe. Aything above 9 or something, idk.
This trick also works for ut2004 unrealed with the lag issue. Modern gpu's are no good for old game engines sometimes.

So if you miss making ut2k4 maps try this trick. Sometimes unrealed will sit there for a full minute waiting to select items or allow you to right click and edit it. A VERY annoying bug. No one has found a proper fix for it.