I think if you mind what you're doing during setup (flush or more) you should be fine...shit, I might have to start counting turns to ensure I don't go too loose...
It is interesting / a bit weird thinking about it.
A normal board you can easily see where the kingpin nut is and that is how I know where to have it so the bushings are just right straight out of the box, if setting up a new set of trucks, eg the kingpin nut one thread down if or when I set up a new board, but this is totally different.
If you are needing the trucks looser the kingpin might be sitting too high, or even come out, or if you need them tighter, can you tighten them down too much and bury into the deck, or run out of thread on the kingpin...
Happy to say my regular kingpins are good where they are, but I can definitely see the use of having inverted kingpins.