There should be no significant alterations made to the design of your system after the design paper is submitted.  This includes structural, chemical, and material components.  Once the design report is submitted, there are no chances for resubmission.  All materials listed in the design report should be present and functional on the system.  However, changes in the quantity of items may be changed – testing and redesign should be done within the downtime before competition so that your system is designed more efficiently.  Reduction in the amount of chemical, the use of lumber, etc. should be looked at and is okay for the final design brought to competition.