I decided to contact PAW International and received the following reply this morning...
Thank you for your inquiry. We developed and supply the TV bracket to Forest River.
The bracket was not designed to support an extension arm and I would not recommend attempting to add one. The equation is force times distance and installing say a one foot arm between the bracket and TV could easily overload the bracket causing it to fail and damage your TV. There are several metal brackets on the market that are designed for your purpose. I would highly recommend using one of these and save yourself from possible damage to your TV.
Considering that the external mount (shown in the picture above) is cut into the outside of the trailer, this isn't good news. Also, i find it interesting that FR would choose a mount like this if it isn't designed for anything but the TV mounted directly to it. Almost every picture I see of the interior of an RV has the TV on a swivel arm of some sort.
I guess I'll look into a different mount for the inside and just not use the TV outside since I doubt I can replace the outside one without damaging the exterior of the trailer.