HVAC with long duct run has insufficient flow
Fixed! Two main issues, one was that the 12” duct was being constricted because it was being squeezed through a small area along with a line for the return. 

The other was that they setup a feedback line from the coil directly to the return. Effectively there were three 12” ducts coming out of the supply, 2 went to the various parts of the house and one fed directly back into the return. Removing that feedback line gave us a ton more air. No blowers needed.