\tab{foo} \input knuth \par

\stoptext

Here, the headstyle specifies a sans font with boldface style, at 1.44
times the current bodyfont size.

However, I want to be able to specify an absolute point size, instead of
a relative size.

I tried variations like

\setuptab[headstyle=18pt]

but that has no effect: the size remains 12pt, or whatever the default is.

If I use
\setuptab[headstyle={\switchtobodyfont[18pt]}]

then the size takes effect (for the key only, which is what I want).
I can combine that with sans:
\setuptab[headstyle={\switchtobodyfont[ss, 18pt]}]

and that works.

But how to mix in boldface?
\setuptab[headstyle={\switchtobodyfont[ssbf, 18pt]}]

doesn't give sans boldface, but reverts to a serif, non-bold style (at
18pt size).

\setuptab[headstyle={\switchtobodyfont[ss, bf, 18pt]}]

gives the same results.

I finally tried

\setuptab[headstyle={\ssbf \switchtobodyfont[18pt]}]

and that works! But it seems clunky: it looks like it requires two font
switches, which I'm told makes things slower.

And I can't help wondering if I'm missing some simpler way.
Is there a more efficient or elegant way to do this?