parametric LED Diffusion & Mounting strip

Inspired heavily by https://www.thingiverse.com/thing:2731338 - but redesigned from scratch to fit IP65 waterproof LEDs:
https://www.amazon.ca/gp/product/B01FFWQCKO

10.2mm inside width
2.5mm inside depth (with 2.5mm radius fillet)

I found a "Diffusion thickness" of 0.4mm is about the minimum (2 layers), but gives almost no diffusion with white translucent filament. 1mm thickness gives a nice subtle diffusion (and cuts down and the harshness

I included the .f3d file with parameters named so others can tweak to suit various styles.