Will swapping out 6 inch flex with 8 inch solve my problem?

[1611mac]

This is our first cooling season in this single story 1800 sq ft ranch style home in NC. The old system died and a new 3 ton 15 seer system was put in (Trane 4TWR and TAM7A). Ductwork is flex duct and was not upgraded.

One side of the home cools much better than the other. A visual inspection shows no "flaws" with the flex-duct, though I'm going to work on it to pull it tighter and straighter.

Two bedrooms really need some cooling help (on sunny side of house.) I was told by the new unit installer that all I need to do is replace the six supply with eight in supply and increase the outlets from 4x10's to 4x12's.

Does this sound reasonable?

How much would "solar film" help (on the windows of the "hot" rooms). There is sun on this side of home most of the day.

Thanks in advance

[second opinion]

This is our first cooling season in this single story 1800 sq ft ranch style home in NC. The old system died and a new 3 ton 15 seer system was put in (Trane 4TWR and TAM7A). Ductwork is flex duct and was not upgraded.

One side of the home cools much better than the other. A visual inspection shows no "flaws" with the flex-duct, though I'm going to work on it to pull it tighter and straighter.

Two bedrooms really need some cooling help (on sunny side of house.) I was told by the new unit installer that all I need to do is replace the six supply with eight in supply and increase the outlets from 4x10's to 4x12's.

Does this sound reasonable?

How much would "solar film" help (on the windows of the "hot" rooms). There is sun on this side of home most of the day.

Thanks in advance

Changing from 6 to 8 will increase your cfm from 75 to 160 if all else is correct Tinting or curtains will help with solar gain

[dan sw fl]

This is our first cooling season in this single story 1800 sq ft ranch style home in NC.
The old system died and a new 3 ton 15 seer system was put in (Trane 4TWR and TAM7A). Ductwork is flex duct and was not upgraded.

One side of the home cools much better than the other.

How much would "solar film" help (on the windows of the "hot" rooms). There is sun on this side of home most of the day.

Adding solar film to 30 Square feet of CLEAR windows on the South or West side would save upto 800 BTU/HR / ~ 1/10th of a ton.
or nearly the same as adding 40 CFM.

[ga-hvac-tech]

There is another issue to consider: Are those rooms comfortable in the winter? If they are, then adding more airflow (larger ducts) will make them hot in the winter. Now one could deal with this secondary issue by putting dampers in the supplies and adjusting them twice a year.

Just making sure the OP considers all the issues he will be dealing with.

[1611mac]

Thanks all for the great answers. Good point about being "hotter" in the winter. The dampers are easily accessible and a tweak between seasons it not a problem. Thanks also all for the numbers provided!