According to official lore, it'd be pretty much the opposite. Apparently, Shinichi's hung.

Base +7, Raiya95 +10, uuumryea +6, AmanoEX +12, Burner405 +6

@BBAGuyver01 every man is small when they are locked in chastity. That's how those flat cages work. They push your erector tissues back inside you so that they can't engorge with blood. So you end up with a flat mound, just like a girl. It doesn't matter how big your cock was before.

Base +10, Burner405 -6