Your best bet would be to substitute using QF, but if this is not possible then follow the dilution sticky to a T the morning of the test. Start running now and pick up some metamucil, you don't need to overload on the water just keep yourself hydrated. Two days before the test just be lazy and eat fatty foods. Continue with the metamucil all the way up to the test it cant hurt. If you follow this you have a fair chance of passing, but if you can substitute i would highly recommend it.