A/c balancing

I have one upstairs bedroom that is consistently cooler than the other two bedrooms. The two warmer rooms are over the garage. A friend of mine mentioned that this might be fixed by balancing the a/c. I have zoned a/c so any changes shouldn't affect the downstairs rooms.
I asked my a/c guy about balancing and he asked if I had the cfm ratings for each room; apparently this is on the blue prints for the house which I don't have. I am pretty handy and I was wondering if the balancing could be done without the cfm room ratings. How do you go about balancing the a/c?
Thanks in advance for any suggestions.
Mark
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Mark Savoy wrote:

Without CFM ratings, without BTUH dissipation for the rooms, it is hit or miss.
There are several things that can be done
1. Restrict the airflow to the cooler bedroom so that a larger fraction of the cool air from the upstairs A/C goes to the two warmer rooms. AC supply houses sell inline adjustable baffles that can easily be inserted into a AC duct to restrict flow on a branch.
2. Run new, larger diameter, insulated ducting to the two warmer rooms.
3. Get a higher CFM fan for the upstairs A/C.
4. Put more insulation under the floors of the bedrooms over the garage. Remember that the cool bedroom has an uninsulated floor and relies on the downstairs A/C to take care of any heat from below.
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wrote:

5. Move any furniture that's blocking the supply or return flow in the warmer room. Take the grill off entirely.
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