i remember subbing to their patreon and reading a dev reply about the same topic; iirc they don't plan on adding bigger peen sizes... i think they intend to keep hiro as feminine as possible
Which doesn't make much sense, because a bigger dick doesn't make them less feminine...
Case and point, literally every other gal-with-a-cawk in the game.
All it'd really do is make the buttsecksin' dished out less of a "small weak dick in big stronk pucker", and more like "you're pounding their shitpit on equal terms". It alters the tone and, in theory, may change the endings to some specific events/plaps.