Bravo4, Your right It's not intended to be carried inverted nor is the Bayonette frog, however the bayonette frog clips on the the yolk main nicly in this position with a little gaffa tape at the other end (the blade tip) the USAF knife fits in side the bayonette frog nice and snug (with a little force) and removes easily again with a little force, it hasn't fell out yet, but I have nothing securing it inside the frog other than the snug fit I thing it will only be a matter of time (may be a strap of velcro may me a good idea here)
The issue bayonet frog was designed to hold the rigid bayonet scabbard. It is not safe to carry a knife in the frog alone as there is no welt inside it - especially if you intend to carry the knife near your chest!
I have seen Goloks being sold with the frog as a sheath, but it that is probably because they are available and cheap. They are not fit for purpose.