Model Guidelines
When modelling your objects in Blender, there are a few things you should notice:
Your models should be created Z-Up, and with 1 Blender Unit = 1 Meter.
For an optimal performance, your models should have arround 5,000 - 50,000 vertices. Do not use the subsurface modifier, it is a waste of performance. Instead, manually tesselate detailed areas. Also keep track of your normals, and work with backface culling enabled:
Also, do not Ignore normals and use setTwoSided in the app. That is another waste of performance. Instead, manually correct the model, or even better, create it correct from the beginning.