Anybody know if image_tests = 0 is case sensitive?
https://gdemu.wordpress.com/operation/gdemu-operation/
If it is not being set/activated, I would expect to see an issue with truncated gdi's as noted above.
fw:v5.20.x absolutely needs image tests disabled, whereas it wasn't required for earlier versions using truncated gdi images (except for Atomiswave titles).
I tested the clonecd image a while back (it was the only clonecd image I could find) and it did work with my clone gdemu fw:v5.15.