I tried to print Arnitel. This was too flexible that the original design can transport the filament, because the gap between the top and the base of the extruder was too high. So I decided to make a new extruder. It is near the design of Camiel. I added a one fix point for the idler holder.
You can use all screws from the original extruder. In addition you need a threaded bar 4mm with a length of even 70mm.
After the print sand the shaft a little that it fits into the hole of the extruder top. Slide it in and fasten the threaded bar with a nut in front and in the back. Put a m4 nut into the knob and glue the knob top on it. I use uhu allplast for it. Take a look at the hight of the hot end brass top. The Extruder base is designed for a hight of 19mm. Maybe you need to drill it a little to meet your needs. For the idler holder you need a 25mm screw for the extruder base.