Kobo Mini Bluefly Back Cover

I've made this back cover for my Kobo Mini, to fit a BlueFlyVario_TTL_GPSv11 and a 5000 mAh battery (link below). I have not put screw holes in the model, as i thought it would be easier to drill them out afterwards, but I ended up just gluing the cover to the Kobo as i could not find the small screws in the right length.

The back cover is made thinner where the Bluefly goes, and where the GPS module is placed I've designed slots in the model for better GPS reception and barometric pressure