try this link?

Here is a link that might be useful: chandy height

I actually facing the same dilemma. I have the entry window that is 64 by 70 and entry size is almost your size and right now think I will order this chandelier 45 in diameter by 55.
Would like to hear from other people experience as well. Thank you.

Here is a model I have in mind

i just got through doing this too. it was super difficult to find because you need a pretty tall chandy to look ok in the two-story, but then most of the tall ones would look too massive for a foyer!
i went with an inverted two tier chandy (with the base being smaller than the top) so that it would feel less heavy when you enter the house. i think my chandy was slightly larger than the rule of thumb recommended width, but it was ok since the larger width was up high and not down low where it would feel more heavy.

Our son has this one: Quoizel MQ5020. This fixture has a height of 60" and the width is 50". The foyer is 12' wide w/ a 17' ceiling. Very happy with the size for the space.