I recently acquired an old 32' extension ladder with a broken flipper and rather than buy a replacement kit, decided to design one in OpenScad for my Printrbot simple -- they work great! The flipper's only job is to move the lock out of the way when you're lowering the ladder, so it doesn't have to support your weight and the PLA material is perfectly fine.See youtube videos on how to replace these. I printed mine at 20% density with an extra-wide brim for adhesion since I don't have a heated bed. Good luck!