I've had a few tiling issues with Speedtree using the sample trees with the provided textures and UV settings. With my own assets not so much, so without really knowing your maps and settings it's hard to guess what's up. My own experience is that ST brings all in pretty well without need of pov-ray as an intermediary (or thru Maya). I tend to create pretty large textures for the trunk surfaces, which is not a 'thrifty' way to spend resources, but TG eats up big poly and large map objects with great ease. The lack of fbx or alembic suport for the imported meshes is a limit for sure, but the obj format works real well straight from ST to TG. The serpentine shaped sand drifts are cool, but from my viewpoint such formations need a more 'open' foreground composition to look appropriate, think of the open wind paths necessary to make such things. I really like the image so far, it's quite a vista!