Nice find. In my greenhouse I have space for only ~15 in-ground trees. There are a handful of trees that I want to keep in containers also, either because they are curiousities (buddha's hand, sunquat, miracle berry) or beause I can't consume a ton of their fruit (lemon & lime). I was wondering how to keep them in check, and grafting the citrus onto an extra-dwarfing rootstock seems like a good choice. Though now that I think about it, I'm not sure lemons & limes are compatible with trifoliate. I'll check the chart before i go grafting.