That looks great, its really cool to see people trying more radical mods like this with 3D printing
Let me just say that I am quite new at RC racing, but part of me wonders if with this admittedly incredibly cool part you are simply swapping one issue for another. The much higher motor mounting position could cause a number of other issues.
Now let me ask something that to some may be obvious, but isn't to me. Why would this compact gearbox be better than the Cream Extreme RC rear weight or even the mid-motor rear weight kit? Seems to me like the weights allow you to move the weight balance rearwards without increasing the CG... But as I said, I may be missing something super obvious somewhere.