Gohan wasn't entirely focused on the battle though, not wanting to hurt his brother. That may very well have caused a drop in Shouki and Yuuki, much like SS4 Goku VS Qi Xing Long after he absorbed Pan. Furthermore, SSJ Goten Baby was unable to inflict any damage on Pan when she wasn't even fighting back, whereas Gohan was manhandling her, showing there's a massive gap between the two, enough that I doubt Gohan's possession by Baby would've been enough of a power up to warrant such. The only attack that inflicted a hefty amount of damage on Gohan was his attempted self destruction, and such techniques tend to amplify the user's power several times over.