Obi scans display bigger because thumbnail images are resized to a uniform width (according to bobo's code). Obis are much taller than they are wide.'
I dunno if we should tweak thumbnail resizing, but we could always "chop" off the obi display at a certain height by using CSS overflow:hidden (that's what I do for the scan displays for newly added and upcoming listings on the front page).
Actually, I have a different idea for the gallery display. There's this nifty
Magnifier effect which is all "hip" and "wicked" and "cool"...