The Ninja-Flex and other soft filaments need more guidance than present in the Wade's extruder. Look at http://www.thingiverse.com/thing:169086 for the explanation. Body and insert for 1.75mm filament. This is not tested. I have made a cutout in the body and made an insert. I thougth it would be easyer to print several small inserts. Print 2 or 3 inserts. The first insert is on the picture, at the bottom of the body. I used my dremel a lot on the insert !