Just make sure that you can still draw other 8x8 sprites fine even if the routine can draw 8x9 sprites. You definitively don't want to have to make your entire sprite data 8x9 just to have one set of 8x9 chars. In the color tilesheets I remade the sprite 8x8 for that reason (and it was even worse, as each 8x9 Reuben char took two 8x8 sprite slots >.<). However, since I used colors, it didn't nearly look all that weird in 8x8 compared to 4 levels grayscale (although this pretty much revived the original sprite >.<).