I had blown-in insulation done in the eighties at my house in California. Loved it. They don't HAVE to drill holes in the siding or stucco, they can go from inside the house and go through the plaster/drywall. I think the inside holes are easier to cover and fill, but might be hard to match paint colors or wall paper. I don't see how they can fill the entire wall space by only removing top siding. Most houses have a cross beam between all of the two uprights that help support the wall from bending. My house had two holes drilled in each 16inch section, one at top and one just below the center line so both top and bottom sections could be filled.