I am not familiar with the williamson line. You might get more responses in the residential HVAC section. The mods don't like us to repeat threads in different areas, but maybe one of them could move this thread to that section for you.
Take care and enjoy the forums.
The statement below is my signature and just my overall feeling towards our industry and does not necessarily pertain to you nor this thread.
There really isn't a legitimate excuse for not doing the job correctly!