Imax b6 v2 lacks the cooling fan of a predecessor model, when using it in discharge mode the ballast resistors get quite toasty
I took a picture of a side panel, remade it in Onshape, and added a simple duct part that fits on the added screw posts. Could've made it fancier, but it works
Fits a generic 30mm 5V DC fan with 24mm space between screw hole centers

Printing: print both parts with PETG or PLA (orientation on pic), no supports needed, any layer height you want (I used 0.28 mm), high infill % recommended for strength (i printed both parts completely solid)

Assembly: thread the fan wires through a special hole and solder them to +5V and GND pins on the edge of the PCB (shown on pic), attach the panel, attach the duct to it, attach the fan with short M3 screws. You might also want to print and use a fan cover

Notes:
1)holes for screws are 2.8mm in diameter, so the screws will cut threads for themselves. Depending on your printer accuracy this might be a bit too tight or too loose, but works fine for me. Use a small screwdriver and don't put too much torque when screwing them in order to not break the posts

2) Duct part should click in place with a tight fit, i used a 5.5mm drill bit to clear out the holes, after that the parts fit nicely.There is a cutout on the side of the duct that allows you to use the barrel jack connector

3) the fan is connected to a 5V pin that is supplied by a L78M05 linear regulator that has a max current of 0.5 A. Having a large voltage difference between input and output will create some heat, but the DPAK body should be able to dissipate it on a large ground plane. My fan draws 0.13A, with a 12v input this means (12-5)*0.13=0.91W of heat dissipated on the L78M05