toddverrone,
About a year ago, while surveying the options for damping the wind reflections I happened on a covering, a perforated plastic/cellophane sheet attached to the windows via the corners with a small elastic band. They looked to be a good alternative. They were European made and with enough searching perhaps you could locate them.
As they were somewhat expensive I passed on them and hung curtains, which I saw were not an option for you. Unfortunately windows are very reflective for sound and make it borderline impossible to get the reverb factor in a room under control.
About a year ago, while surveying the options for damping the wind reflections I happened on a covering, a perforated plastic/cellophane sheet attached to the windows via the corners with a small elastic band. They looked to be a good alternative. They were European made and with enough searching perhaps you could locate them.
As they were somewhat expensive I passed on them and hung curtains, which I saw were not an option for you. Unfortunately windows are very reflective for sound and make it borderline impossible to get the reverb factor in a room under control.