It is true that fp2.6 an VFP7.0 dbf's are different. Only in header Microsoft pu a few simbols that set with what product you work.
My programmers tell me that if you open a DBF's with other version - it change header and could be not possible to open it with original one.
We refuse that kind of project where client like to work simultaneously modules done with FPW2.6 and VFP7.0