Can more than one extension be used together?

A contractor says:
Can these 4" extensions (39-157) be used together to create an 8" or 12" extension? I have a Kitchen boxed bay casement window that is hard to reach from the sink and need an extra 8-12" reach to operate the window.

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Dave Sr. from SWISCO responded:
I myself have not done it, but checking out the product it does look like it can be done. However, I would suggest ordering the support bracket 39-157B to go along with it for added support.
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