I saw this somewhere and figured I'd make my own and I made some improvements as well. For starters, there is a plug piece that goes into the stick and then seats up against a shoulder to give you a smooth transition from stick to 3d printed end. I also made the edges of the top piece smother (added a round-over).

Update - 07/17.2018
V3 is out! This is a couple small but good updates. I made a few adjustments to the plugs so that they taper and are easier to get into the stick. Hope you all enjoy!

Update - 07/01/2018
This is the ready-to-print version! The pieces are all REALLY snug so you may have to file down the inside of the stick to get everything to slip in. Otherwise, this thing works great!

A few tips:
-Cut as close to the butt of the stick as you can. As you get further down the stick, it starts to taper and the pieces don't fit quite as well.
-For length of pieces, print all 3 pieces, lay them out and put a regular hanger on top of them. Then measure from the ledge and cut the 2 shorter pieces perfectly identical, put those pieces together and then cut the bottom piece. I found that this give a better result than trying to cut to pre-determined lengths.
-I have included a cut guide that you can print out as well. This print guide is roughly 1/2 from the side to the slot so you can mark the stick with a crayon, then measure 1/2 inch out and put masking tape on the stick. Then the cut guide can butt up right against that tape while you start your cut. I would suggest using a mitre block though as my cuts were freehand and came out a little less than 90 degrees (easily fixed with a dremel but better to make a good cut the first time through).

If you have any questions or suggestions, please let me know!

Enjoy!