DO NOT INSTALL A 2X3 OPENING FOR A 3X4 DOWNSPOUT
Snyder's Seamless Gutter
With a good wind, this downspout will blow off. Keep it snug to your house.
This gutter should be longer so the water doesn't overshoot the lower gutter.
When connecting your downspout to underground, make sure it's not full of debris. Good remedy . . . gutter topper.
Make sure your downspout opening from the gutter is as large as your downspout.