I'm still running on the edge with this set up. I think a 6 inch system would do much better and give me some head room to work with.
The exhaust intake needs to be as close as possible to the ceiling as possible (where all the hot air is)
In the pic it looks like you have it on the floor where all the cool air is...
Your cool air should enter the room as close to floor as possible and as far away from the heat exhaust as possible.
This way you have cool air coming into the room from floor level, moving across your room, and the hot air is removed efficiency. Good luck.