Reedo,
I've found that it's important to transition them from higher humidity protected conditions to outdoor conditions gradually. I live in a pretty mild, humid microclimate and the week I moved a couple that I thought were ready outdoors to a shady spot, we got drying winds and the leaves dried out and plants did not recover. I think it can be deceiving that the plants are established and ready to go outside even without much root growth if they are growing under humid protected conditions. I would not rush it. I have noticed cuttings (not Yangmei) can have new growth for weeks without any roots. When I move my plants outside, I put them in a shady spot under other trees and a banana plant for increased humidity. The thing you have to watch out for when you put them outside are tiny caterpillars that will eat tender new growth, I check daily. Nice that most of your plants have made it. Good luck.
Janet