I have an old (but very good) W9INN 40/80 dipole. The only problem is
it is cut for the upper phone band (centered at ~7.200) for 40 meters
and I now do most operating in the lower portion of the band and would
like to move the center to about 7.100 MHz. The 40 meter portion of the
antenna is all soldered so I cannot just unwrap and extend it bit.

Any suggestions on the best way to add a extension and how much to add?

I have been thinking about cutting it and soldering in an X?-inch
splice. Does the extension wire have to really match?

Dick AA5VU