I think the "times" in
```
...the grid spacing times `kmax_factor`.
```
feels wrong, or perhaps misleading.  I think I'd agree with "and" or even "divided by" rather than "times", or alternatively (and to be totally exact) we could say `...the grid Nyquist frequency times kmax_factor`.  (there we'd be using the precise term Nyquist frequency rather than Nyquist rate: http://en.wikipedia.org/wiki/Nyquist_frequency)