Seems like a good idea to try to incorporate a sound system (& possibly a DVD player, etc.) into the "box" while I'm replacing the TV. Was just thinking of DVD, etc., storage behind the TV as it seems I never have enough storage.
Will need to look at the TVs enclosure to see if mounting the new TV on a 'flap' or directly to the base as you did is the better choice ... both good options but yours is obviously the easier to accomplish.
Adding a sound bar &/or DVD may also make the 'flap' idea a little less workable ... gonna have ta cogitate some on this
I have an air vent behind the TV (up by the top of the windshield) and a vent on one side of the box so ventilation should not be too hard to insure even if I add a sound bar, etc.
Thanks again for the ideas/information, Gasman6674!