NetworkTransform - interpolation?

I've got NetworkTransform working between server and client. Setting the Network Send Rate to 1 sec does exactly that, my objects position gets updated once per sec on the client. Oddly, you can't set this number to a smaller value on the editor, but I can force it from script to e.g. 1/30, in which case I get more updates - and more data traffic.

Question: How do I enable position and rotation interpolation with Transform Sync Mode == Sync Transform?

As a side note, releasing a new...

NetworkTransform - interpolation?