Fitting a Vinyl Replacement window in the Rough Opening

I am installing a vinyl replacement window (30 1/4 inches by 44 1/4 inches) and the rough opening is 30 3/4 inches by 45 inches. I have taken out the old window and I have fit the new one into the rough opening.
My question is: Does the new vinyl window allow for extension left to right and top to bottom to make it flush with the rough opening? Is there a screw(s) to modify the dimensions of the window once the installer has it in place. I know I have to caulk the inner perimeter of the window once it is fully installed.
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You need a good pair of shears or cutter and maybe a hacksaw. That plus plenty of caulk will make it look like it fits.
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When I had mine installed, (aluminium replacements, not vinyl) the installers had 10' long sticks of aluminum with a white baked on finish. It was about 1 1/2" tall with a 1/4" foot on one side, kind of like asymmetrical angle iron. They got them level and plumb then trimmed them out with the angle aluminum. It sounds more crude than it looks, I'm actually pretty happy with the job.
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Vinyl replacement windows that drop into the original frame are typically sized 1/2 to 3/4" smaller than the opening. The outer sash stops in the frame should have been left in place. These stops plus caulking will cover any gap on the outside. The inside trim should have been removed before the vinyl window was put in place. The side and top trim is then reinstalled, covering the inside gaps. Also, most come with a top cap that can be raised or lowered to cover any top gap.
There are side adjustment screws in these windows.They are only to insure that the sides of the frame are plumb. The screws are turned in or out to eliminate any bowing.
Most of these windows, if they are sold by H-D or Lowe's, etc, come with an instruction sheet that explains the above. Even if you don't buy your windows there, you can pick up one of those sheets.
Doug
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