When you pay full price up-front, you lose all control.

I think there are enough of you guys who buy jets from China to force a change in the way you do business with the manufacturers. Just say, "NO, I won't pay you ANYTHING until the model is ready to be shipped, and proof of readied shipping documents are provided." Of course you still have to worry about broken items being sent (cracked canopy, frame, etc.)

Make the purchase under your terms, OR else there is no purchase. They will begin to understand when they don't get orders under their terms.

All they want is your money. Once they have that, their service is non-existent. Haven't you noticed that?
Damn! You don't even get emails from them after that. OR you wait weeks for an evasive answer, or a BS excuse of being too busy!

Demand better, or just stop buying.