One-sided pentominoes fence

The set of one-sided pentominoes.

Use the one-sided pentominoes to form a fence that encloses an area as large as possible.
The pentominoes must be placed on the same plane, and they must touch along the full edge of a unit square and not just at the corners.
This solution was made as an example by Ben De Vreese en Mike Coffijn from KSO Glorieux Ronse, BeLgium

Do you have our excel file to draw the fence? You can download it here.

'FlatPoly2', a programm by Aad van de Wetering, can be of great assistance when trying to find a solution. It can be downloaded at his site .