Sounds fun and I would try the upside down position as a temporary position to see if you like it this way or if it sounds better with the more standard tweeter on top position. If you are adding an extra baffle you could also allow for some slight downward angle towards your listening poisition. Maybe try to have the tweeters aligned with the midline of the screen.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70