I remixed the original design from Ricardo Coelho.

1) Added a PDF with lines on how to fold the wing. See also the original design page. Depending on your printer it probably is best to print it at “A4 without borders”.

2) I made the slot for the wing wider. I printed it on 90 gramm paper. You might have to use some glue.

3) Made the tolerances for the body tighter. 

After printing and assembling you have to experiment with “elevators” and center of gravity. But that is the fun of flying paper planes.