Unless dumb, any Contractor will be able to generate a schedule to his benefit. If you are a Contractor don’t waste the opportunity it is at the beginning or never.

Some tricks that reduce float will be obvious but others such as the use of multiple calendars can be harder to discover, especially with software such as P6. Is just a matter of using fields not disclosed by digger file comparison.

Remember it is the Contractor who will create the schedule, it is supposed to be his own, most will create two versions, one for contract management tailored to his benefit and another for his use.

Once accepted then the Owner falls in his own trap, especially if he does not allows the Contractor to make changes to the logic.

A wise contractor using P6 knows calendar holidays can be hidden and changed at will during prior updates without the other side noticing as P6 digger will not disclose such changes then he will have the Owner at his mercy, and this is just one way of many others. This asumming P6 is as bad at this as old P3e version of P6, the original.

The more complicated the schedule the easier to hide these tricks. I would recommend you use as much named resources as you can each with a particular calendar, this will make it extremely difficult if not impossible for the other side to detect holiday changes on hundreds of resources each with a particular calendar. Also subdivide the network in as much activities as you can and use resource leveling to drive the schedule this will help you to hide the tricks when resource and calendar related. Limited resources drive most schedules and the fact that resource dependencies are ever changing will drive crazy the other side analyst, many of them old school analysts incapable of efficiently dealing with the subleties of resource constraining.