X3 on what John and Mike have said.
I had the same concern, and finally contacted Jayco directly about it. Their answer was no, do not add support to your slideout. I also asked about the weight capacity of *my* slideout, in my Jay Feather 23RLSW, and I was told it's designed for four 150 lb. people, or 600 pounds. That may not apply to your specific model, but it's worth asking Jayco because it's not in the manual that I can find!
TV 2010 Ford F-150 Supercab
TT 2016 Jay Feather 23RLSW