I used a spreadsheet to come up with the single multiplier of 15%.  Was hoping that having just that one allocation, ProSeries would be able to handle the divvying up of the indirect expenses.  However, it does not seem to want to accept the % overrides I'm putting in the Expenses section.  It allows me to enter the %, but then completely ignores it when calculating what should appear on Sch E as an expense.  I really expected better of this program.