Journeyman,
I do consulting for a few books and here is the percentages my company recommendeds.
30% to 40% in Western Union/Neteller
10 to 20% in credit card reserves (rolling reserve is OK)
30% to 40% in a bank account for wires and checks.
They should mark to market (adjust the percentages weekly to account for money won/lost by players). In addition there should be backup funds equal to 50% of deposits which do not need to be liquid but should be able to be turned into cash within 7 business days.
Good Luck to All