Lipo mount for electric skateboard

Note!!!
this part broke after a few weeks of use - https://goo.gl/photos/5fpRg7m1fgBkHXUp9
I designed a much more rigid alternative - http://www.thingiverse.com/thing:2163117

This is part of a project in which I converted my longboard into an electric longboard for my kid. I mount 4S 5200mAh lipo on it for the kid, but it can hold 2 or even 3 packs stacked if you don't mind the hight. There is room for velcro straps on the sides, but those are not needed when mounting a single pack.

Ther