OK to use plywood instead of hardieplank between two close windows

siding

I'm installing HardiePlank siding to a sunroom. It has lots of windows and some are very close. I'm using the method of putting the white trim over the Hardie Boards not beside them. (This is the way a contractor previously did our garage you can see in the background.) I will be putting trim around all the windows. These close together windows will have just this trim showing between them.

I'm wondering if I can get away with just putting plywood between the close windows instead of little pieces of HardiePlank as they'll be fully covered with the white trim anyway.
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Best Answer

Yes, but I’d use an exterior plywood product made for that type of application, like Medium Density Overlay (MDO) plywood and I’d be sure to pre-prime the edges. That is to say, I’d paint primer on the edges before installation.

In order to seal the window edges and building paper, I’d use a peel and stick seal tape.

Jack is correct that trim is customary for spaces up to about 11”.