Scheduled Billings lines require use of dates and Impact WIP. It would be easier for users to be able to enter the contract value on the project card and/or the task cards. If they want an overall contract value then on the project card. If they desire to enter contract value for specific tasks, allow this on the project plan screen
WIP is challenging on Fixed Price because of the dates of the billings. It would be easier if it was based on a specific field.