Hey Khoa, I think garlic may be a tough target as it can have quite a varied amount of peel and husk, I will listen out with interest on how you do.
I was surprised with green leaves, that the SCiO would shine right through them, and give slightly different results depending on what was below. Two leaves thick is my standard for the moment. Conversely it does not change the scan very much if I have the leaves upside down.
I am sure we will learn a lot of DOs and DONTs in the next few months.