greg, the editable area on a Pronto (get rid of the home, macro, device buttons) is about half the 6.5, so at least from a diagonal point of view, they are comparable. but I don't think that they are the same shape, assuming the ipronto is 4x3 that will give 5.2x3.9=20.28 in area, also the Pronto is around 2.4x2.2=5.28 =.21 square inches that are lost.

Basicaly each 1/4 should be about the same size as a Pronto screen (and since the Pros screen is a bit smaller, it might actually be bigger), so you should be able to fit about as much as you fit on a Pronto in a quarter screen.