Downspout Cap for Hydroponic System

I made a Hydroponic system from a downspoutwith a 2x3" opening.

https://www.instructables.com/id/Balcony-Recycled-...

The end caps need a clean-out. There is nothing to use that is off the shelve, so I designed my own to 3D print.

The plug is red and the cap is blue for illustration only. I would print in white abs to match the downspout color.

https://www.tinkercad.com/things/jn1oevuZH7c-downs...

The end is tapered to help with a tighter fit.

I use Marine Glue (5200 adhesive)