It sounds like you've got T-111. It's just cheap fir
plywood with grooves cut in it. You certainly can
piece in a section, but that would look pretty tacky
and might eventually let water in. Also, how are you
going to get a good cut on the piece that stays on
the house, especially cross-grain?
A new sheet is not expensive and the job is not
very involved. If it were me I'd just replace the whole
thing. Otherwise you might spend more time and money
in the long run trying to "patch your patch".
| One of our siding panels (plywood with vertical grooves) has a section
| that is "squishy." It's not a full panel, as it has a window opening cut
| in it. Even assuming that a replacement panel would have the same
| texture, would it be OK to cut the old panel right below the windows and
| "splice" in a new section (and caulk the joint), or is it essential to
| replace the whole panel, which means removing the window casing etc.?