[texhax] Explicit inter-sentence space?

[Karl Berry]

    > I'm still mildly curious about how to input a space of equivalent size
    > and stretchiness to an inter-sentence space.

    \spacefactor\sfcode`.{ }

That seems best, but somehow I feel compelled to mention
\fontdimen7\font, where is where the "extra space" after-sentence amount
originates.  (Appendix F.)

karl