Wonderful test, Steve. You got the hang of ST real quick.
You could try adding an empty surface layer after the default flower node, pull another line to a desaturation node plugged in as child, add a PF and a transform shader set to world as mask for the desaturation node and/or the surface layer. If desaturation node is not masked by PF + transform let it have a constant white.
These settings look okay to me, maybe a bit more translucency, but that wouldn't do much I think, as seen here from above without much light passing through. Did you lower opacity?
Detail setting can be lower, as there's not ground visible.
Oh, and textures for tgo"s don't need to be all in the same folder, as long as they stay where they are.