A few days after the installers left, I looked in the roof space and found they had split one truss/rafter almost the entire length and other trusses/rafters had also sustained damage. This structural damage could have been avoided if they had pre-drilled the hardwood first. I sent off photos to TVS at their request and after a week, not even a formal acknowledgement of the issues, let alone starting remedial work. In addition, I was told by TVS that the installer could install the extra switch in the mains switchboard but when installer arrived, installer knew nothing about it. Had an extra expense to get an electrician in to upgrade.