Max Load Factor?

[cnrussell]

I was trying out different configurations on my fleet of 732's, and found that if the flight sold say, 100 seats in a 120Y config, it would only sell 90 seats in a 5C-108Y config, using the same flights. The load factors average about the same before and after, typically in the low to mid 80s. Is there some sort of cap on the load factors? Will people not buy the last 10% of seats regardless of a/c type or configuration?