Style question: Correct bass or correct function?

Hi folks! When submitting a TheoryTab, it’s not always possible (AFAIK) to choose any bass note for a given chord outside the triad or the 7.

So here’s my question: I’m working on a tab in C major with these chords:
C, Bb(add9), F
…and bass:
C, C, F.

The function of the Bb chord is IV/IV. But Hookpad does not let me write Bb(add9)/C. So I have two imperfect choices for the Bb chord, as I see it.

  1. Lie about the bass note. Input IV(add9)/IV.

  2. Lie about the chord’s function. Input something more convoluted.

What is the preferred style?