R17 does not state that you cannot use designs from before kickoff. It does state however what other things you can and cannot use. By the fact that FIRST is very diligent in how it writes its rules I would think that the omission of stating that the design was not illegal was by intent. This would mean that designs would be legal but the fabrication must be done during build season. R18 states that design and fabrication are to be done during build but does not state the design from pre kickoff is not allowed therefore it should be allowed.
Just some thoughts to ponder.
