if you can settle with doing it so it only comes up to under the ribs it should be fairly straight forward but otherwise you may have some bracing and bowing issues as the ribs are there for strength.
just cut your window and cut the acrylic (better for the flexing this tank will be susceptible to) 1.5 inch or more over sized on all sides and then create two stainless frames that will be drilled with the window to sandwich the the whole thing together. Use silicone as well to seal the window