Cool stuff man! I need to start printing more hollow models too, the difference in quality is huge at times and I don't need the strength that the infill give me.
The only thing I see that you could improve on is your first few layers; do you heat the bed while printing? If not; you could try printing a larger 'brim' for the first 5 layers, just to give your layers some time to cool down. Or simply print an object next to it that's only 0.5mm high.

Haha, I thought exactly the same thing about those ping-pong balls!

I am the one that's happy being talked into a Flashforge; the options to mod these things is great and for the cost they have a very good quality (aka great bang-for-your-buck!)