Air-Duct Cleaning

I know on a lot of RV's the ceiling ducts are nothing more than channels cut in the Styrofoam insulation. I would think a rigorous duct cleaning with long wands/rods etc might tear up the Styrofoam. On the heat ducts I also imagine that the ends are not screwed in like solid duct work in a house. Most is probably flex tubing and hose clamped or zip tied on. Again I would exercise caution here so as not to perforate the duct or pull it from any connection. Things you may not know when damage is done let alone fixing it if you do know.