I have received a few questions regarding the MS wood fab CDE. All of them pretty much center around how much flexibility is allowed with the design.
I understand the desire to make a project better and applaud the efforts of your students. Let me point out an item or two that may clarify your questions.
The project must meet design specs. This means any deviation from dimensional values will result in deductions or disqualification depending upon severity. This does not stifle creativity as different finishes, fasteners, or even wood species may be used.
Certain wood species come in varied widths and thicknesses so make sure they are planed/cut to match the plan.
Edges may be rounded over without changing dimension. Do not add anything like tile which would change the plan.
This is not an exhaustive list so if you have any questions please let me know.
I hope this will clarify any questions you may have.