No problem, I saw this on the Milviz general forum:
"It flies in P3D v4.5 but I don´t see the pilot 3D figure. Overall I would say it works fine (I never tried in earlier versions to be able to detect failures).
When you install it, as P3Dv4 is not detected, installer will extract files to a temp directory. In my case it was in F:\temp0. Just copy the content to Effects, Gauges and Airplanes. Don´t overwrite files as the ones already installed would be most likely newer than the ones in the Stuka. Alternatively you can use 7-Zip to unpack the exe directly.
Autostart is not working completely, and fuel pumps are not switched on, so a periodic engine start sound will be heard. Just do a cold and dark manual start instead or check that all systems are on after the autostart."
I used the installer: MilViz_Stuka_v3.170417.exe. I don't remember having to copy any files out of a temp directory. But installed it outside of the main Prepar3D v5 root. I didn't care if the crew was visible or not, but if I remember right there was a spot on the external model (view) between the pilot and back seater on the fuselage that I clicked out of curiosity (the mouse changed as I went over it) and both figures appeared.