Garmin Montana Kayak daybag mount

A mount to attach a Garmin Montana GPS to a kayak daybag closure. Remixes the mount itself - dxf files have been used without changes, while montana_arm_set.scad and montana_attach_plate.scad have been extracted from the original bike mount project with a few minor changes. Many thanks to MoonCactus who generously provided the source files and allowed remixing.

fillet_cube.scad is from my openSCAD Primitives library (http://www.thingiverse.com/thing:1679551 or https://github.com/imageguy/open