Hello and once again thank you for bringing the 64 to degrees of quality it never touched - talking here especially of the attention in converting the inner workings of the original Pac-Man masterpiece.
I dare to provide a suggestion about the scrolling - not coming from me but from Namco:D
Please check what they did in the Game Boy version. Focusing on vertical axis, they start doing a overscan scroll much earlier (64 pixels from the level border or so). This makes the scrolling feel less abrupt, and starts revealing a bit earlier the not visible area.
(And of course sorry if you already considered this option and ruled it out because reasons!)
That said: you rock. Have a nice day!