Hey, guys--
that far the vertices get "wrinkly" (see pic), which doesn't make sense to me. It has a fuse early up just to make sure things are, well, fused, but otherwise it's just a scale to fit by match size to get it 2 units high. (I've also tried scaling with transform, which shouldn't--and didn't--make a difference, and also packing it in case treating it as one point helped, which it didn't.) Any idea why this is and how I can get the scaling to behave? Here are pics with it scaled and the same area at full size.

ARGH--addendum: Viewport was apparently screwy. I restarted Houdini and now it's behaving.

it might related to OpenGL precision. try do a simple render to see if problem remain. if render has no problem. than try adjust viewport camera near/far clip. near not too low,far not too high.

It looks like a displacement shader to me. scaling it down could make the displacement out of scale for the new size if not corrected.

Thanks for the replies--should have put my above addendum as a separate comment to make it easier to see. The problem was that the viewport needed to be reset, that's all. I wouldn't expect that to cause this issue but, well, it's working now.