On our 2002 DSDP we had two screws coming in from the bottom of the box into the frame and two at the top that were hard to see into the roof panel and frame. After that, the TV was held by two brackets into the roof panel that were screwed into the top of the TV. Not sure if they used the same setup on the gas units though.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '14 Jeep JKU Dragon Edition