HVAC option help

[bluecord]

My first floor ducts measure 5" across and are flex. Assuming everything is sealed and no kinks will this be adequate for a 2 ton system with variable speed blower? Only way they could be changed involves tearing into the ceiling. I would like to post some pictures but am having trouble. The pictures are on my computer and the image inserter asks for a url. Any ideas?

[beenthere]

7-5" flex runs is a bit small for 2 tons.

[bluecord]

if I sized up the attic ducts to 6 or 8 inch would that help?

[beenthere]

if I sized up the attic ducts to 6 or 8 inch would that help?

How many would that be.

[bluecord]

There will be four duct runs upstairs and the four downstairs.

[beenthere]

4-8" and 3-5" is enough for 2 tons.

[bluecord]

Will my airflow be unbalanced because of the larger duct work upstairs?

[bluecord]

These are images of my downstairs ducts. Am I right in thinking the spots are mold?

[beenthere]

May or may not be mold.

In the summer, you want more air flow to the second floor. That last pic, the air flow is restricted.