The Bear upgrade for the Prusa MK3 is a wonderful bit of work ( https://www.thingiverse.com/thing:2808408 ). It now comes with some nice reverse Bowden adapters that attach to the Bear's v-slot frame. These adapters work great with the tee-nuts that come with the Bear kits, however they aren't compatible with the spring-loaded roll-in tee-nuts.
The spring-loaded roll-in tee nuts ( http://a.co/d/dPHTUTz ) are really convenient for adding things to your frame after you've got it all together. They don't require removing the end from the v-slot, and because of the spring they stay in place wherever you put them while you screw in whatever your'e attaching with them.
The Bear accessories have a 1.4mm deep v-slot profile, and unfortuantely with these tee-nuts, there just isn't enough room. While this deep profile is a good idea for structural parts, it isn't needed for things like the reverse Bowden adapters. So I have remixed these to use a slimmer profile which is compatible with these tee-nuts (It took me longer to type this than it did to make the change).
I've also included an extra adapter that I use to route the PTFE tube from the bottom of the frame to the top.
NOTE: This is a remix of 2 parts that are not on Thingiverse. They can be found here: https://github.com/gregsaun/bear_extruder_and_x_axis/tree/master/optional_parts/reverse_bowden
3 perimeters, 5 top/bottom layers