Stackable coverings with overpowered lift systems and related systems with hold-down brackets

A covering for an architectural structure, the covering being movable between a retracted position and an extended position, the covering comprising:

• a headrail;
• rail;
• a bottom rail supported relative to the headrail;
• at least one stackable covering element positioned between the headrail and the bottom an overpowered lift system configured to provide a lifting force that raises the bottom rail relative to the headrail towards the retracted position of the covering, the overpowered lift system comprising:
• at least one lift cord extending between the headrail and the bottom rail;
• a lift rod coupled to the at least one lift cord;
• a variable torque motor assembly operably coupled to the lift rod, the variable torque motor assembly configured to apply a variable torque output to the lift rod as the covering is moved between the extended and retracted positions;
• and
• a booster spring motor separate from the variable torque motor assembly, the booster spring motor configured to apply an additional torque output to the lift rod independent of the variable torque motor assembly;
• and
• retention structure provided in operative association with the bottom rail, the retention structure being configured to engage at least one hold-down bracket to hold the bottom rail in position relative to the headrail against the lifting force provided by the overpowered lift system;
• wherein:
• the variable torque output applied by the variable torque motor assembly is balanced relative to a base torque curve for the covering representing a torque demand for the covering as a function of a drop length of the covering;
• and
• the additional torque output applied by the booster spring motor provides a torque curve for the overpowered lift system that exceeds the base torque curve at each position along the drop length of the covering defined between the extended and retracted positions.