I saw a japanese pro talking about handicap for a smaller board size, specifically 13 x 13:
“13路では置き碁より逆コミの方が面白いゲームになると思っていまして” (translation: I believe, in 13 board, reverse komi makes for a more interesting game than on-board handicap.)
His article does not mention a method for calcing such reverse komi for 13 x 13 though.
For 19 x 19, the following article links to 2 ways to calcing reverse komi, one is a table made from game data, the other a formula using ogs rating.
https://senseis.xmp.net/?ReverseKomi
In theory, someone versed with data mining could make a similar thing for smaller boards as well.
EDIT:
the following is a discussion about handicap vs reverse komi. there is an interesting comment wrt their effect on a game.