Drilling Drainage Holes

Good job! I would have hesitated to drill an antique myself, I admit. But I have drilled a number of stoneware and lots of porcelain in the past. I would have suggested diamond bits but I see you already had that idea. That's what I use myself and I find they work much better and cleaner than more conventional 'ceramic' bits.

I've drilled several inexpensive pots, I always drill from the bottom, they usually chip when the bit exits the hole,so that will be under the soil.