Your question cannot be asnwered as stated. If PERCENT is USAGE DISPLAY, the variable will use 8 bytes. If PERCENT is USAGE COMP, the variable will use 4 bytes. If PERCENT is USAGE COMP-3, the variable will use 5 bytes.
Moving the implied decimal point will NOT change the length of the variable. It may, however, cause you severe problems unless ALL the data is converted to the new format at one time. Since the decimal point is only implied and not actually present, 12345678 would be interepreted as 12345.678 with one PIC and 1234.5678 with the other PIC. These values are not the same, even though the underlying representation (12345678) did not change.