Ask an expert. I went to Sunrise Yacht Products of St. Pete, Florida, for answers. They make excellent tramps for cats large and small. Looking on their website and going home/product info/border material leads to this quote:

We recommend, and use, the Gore-Tex Tenara thread in all the exposed stitching on all of our nets. We do however offer Beach Cat trampolines with the option of a lower cost polyester thread. The Gore-Tex Tenara thread is made of 100% PTFE, and is completely impervious to UV degradation and other elements found in the marine environment. W.L. Gore & Associates, Inc. guarantees their thread will outlive any material it is used on. The importance of this cannot be understated, as any net with a border relies on the strength of the stitching to hold it together, and thread made of all other materials deteriorates in the sunlight at an alarming rate.


% Strength Retention vs Days of UV Exposure


Guess that sums up the polyester thread issue. Don't do it!

Sunrise Yacht Products