I just received my dizi, and the protector fits perfectly. I changed the diameter to 24mm for my dizi, even though it measured 25mm. You may need to adjust it similarly for yours. You will need to install OpenSCAD if you don't have it already, measure your dizi's diameter near the dimo hole and update the "dia" variable. Then you can adjust any of the other variables as you see fit, press F6, wait, and when it's ready, do File | Export | .stl, and you have a new STL file to print.
I print this standing up, but if you prefer, you can print it lying down. No supports should be needed either way.