What do you consider a lot? I was thinking 6-8 and would rather have 6-8 cfls than 4-6 four ft bulbs. I have seen 55 gallon tanks with four cfls mounted vertically that have no problem lighting the tank. My 77 is the exact depth of my 55 gallon, only difference is two feet more length.
I have little interest in staggering four ft shop lights. The point of the cfls is to have a clean uniform system. If I need to create a reflector this isn't a problem either.