Totally doable, especially since you have figured out the trim and finishing inside and out.
But why not wait for something that fits? Is it more expensive for the actual window size? I buy my windows from alside, and they are all made to order and when I have priced them out, they are cheaper than HD or Lowe's. Go find a new window supplier.
Alside does not sell retail, only to customers with an account, think larger volume/contractors, etc. you may want to start making these connections if you continue to buy properties.
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