I might be new to robots but not new to using the technology around 3D printing, printing in Nylon would be a much better alternative to using other materials, but i do think that structurally the 3D print will not hold up should the machine take one huge knock, de-lamination regardless of material used is still a critical factor (given some of the FW's sizes, shapes and weights along with the shear damage they can inflict) or awkward landing.

I could suggest 3D printing using one of the metal compounds available should your printer be capable of using these, as their tensile strength is greater than Nylon.

However that said... and not to take anything away from you in terms of ingenuity but...couldn't the mounts be made up using blocks of HDPE and just have then CNC'ed, or for cheaper options since its relatively a simple structure, a block made up of the right size and using a pillar drill, forstner bits and drill bits in various sizes which will in turn provide a much simpler quicker, cheaper and yet stronger mount?