Parallel Polarized Pentominoes

Puzzle description:
Parallel polarized pentominoes consist of five unit rectangles instead of squares each. Hence, they allow only 180 degree rorations and flips, no 90 degree rotations. This increases the number of pieces. There are 21 different polarized pentominoes, they fill 105 unit rectangles and can be packed in large rectangular trays of size 5x21 and 7x15, each in both possible orientations. Other, more irregular trays are possible.
The STL files given here provide the 21 polarized pentomioes and a 7x15 tray.

For more information, see Peter's Puzzle and Polyform Pages: http://www.polyforms.eu/pentominoes/parpol.html
If you can read German: Mehr Informationen gibt es in https://welt-der-geduldspiele.blogspot.com/search?q=3D-Druck

Puzzle difficulty:
The puzzle has a very large number os sulutions (if you know the exact number, please send me an email). This increases the probability that you can find one.

Printing instructions:
The model STL file was generated us