Update: Finished the bowden carriage for this check it out: https://www.thingiverse.com/thing:2842554
I know some crouchy people will tell me how this will cause vibration due to the spool being on the top. Well some of us do not have the space to mount the spools in a different location. Instead I came up with this idea. I have tweaked the design since I printed my own. It will now sit to the right, so no overhang! The extruder will sit further forward so you can get to it easier.
The gap between the two bars (internal distance) is 110mm I found this was plenty of room for even the widest of my spools. It is just high enough to clear the extruder and since I moved that forward you will have ample space.
I made the arms with hex holes so it doesn't eat up all your filament. I know it seems overboard on a few parts but it's 1kg up there and if it falls down onto your printer...
I used 4 bolts on the left arm since it is only anchored to the main section. You could get away with two bolts if you install them diagonally. To the right is the big frame brace which includes the slot for the upright bar. There are two holes in it. One is hidden behind the top plate of the anet. It is counter sunk in quite far so it will not touch the acrylic. I liked the x axis brackets by Leo_N but it had unnecessary plastic around the hole. This means mine can be installed without having to redo all the cables! I also included the opposite frame brace with my addition.
(Leo's Original: https://www.thingiverse.com/thing:1872162)
You will need:
4 x M3 bolt (22mm at least)
2 x M3 bolt 30cm
6 M3 Nuts
I used 40% infill to make sure it had enough rigidity.
Do not use supports on any of the bolt holes!!
The only support you need is on the large hole for the extruder. I purposely designed it so you can print all but that easily.
Print the two support rods flat so they only stand the 10mm off the bed. You need them to print that way so they have a lot of strength. If you print them standing up they may snap as it would only tape one layer to snap it.