If you land (or attempt to) a PA 28 in a 30kt crosswind I would imagine you are in uncharted territory, did not the test pilot only demonstrate it up to 17kts?
Yes, it was demonstrated at 17, not limited to 17.
I've landed one in a 25 knot crosswind without any drama. It was a steady wind. (I am just a regular PPL, no super hero skils.)
Also agree with Whopity about using full flap where possible, although I might take the final stages quite late, to keep a little more lateral stability further up, where there may be stronger gusts.
Nonethless, being current on flapless seems to be sensible, any mechnical system can fail (one hopes, symmetrically.)
Flapless landings in a PA28 are really not a big deal nor very difficult - speed control on the taper wings is important, but that is the same for all landings on these aircraft.
The OP asked a precise question about the incremental distance, for which there is not a POH answer unfortunately, IIRC.