Yes, no kidding. I'd like to know how the main TV mod goes as well. Been thinking I making that mod since before I bought the RV!
Other thoughts of mine on that subject:
The TV while slid out will experience greater than normal stresses since you are moving down the road, so maybe get a beefier than otherwise required mount? Maybe put a support of some sort on the fridge side to help carry the load when extended? Also, make sure the mount is secured to very sturdy parts of that built-in cabinet.
Kids or the DW may bang into the TV while extended. Extension/retraction should be easy to do even by the kids to allow access to the bathroom, though I guess they could crawl under. There should be a lock to keep it from sliding out unintentionally.
On the plus side, you can get much thinner LCDs nowadays that are also probably lighter.