AV8B is a little touchy , but in the flight manual , we can see it dont love Negativ G's . in a dive you don't must to push forward your stick.
In pocket guide , Prohibited manoeuvers , see the graph , beetween mach 0.8 0.9 , AOA max 10 .
or 9) under 1 G for more than 15 seconds .
Maybe Flight model need more tuning , i dont know ;)