Not having an HVA/C vent in my toilet closet made a hugh impact. My master bathroom suite also has a whirlpool tub and a shower to go with 10 foot ceilings. After about three years, I notice mildew on the ceiling of my toilet closet. The moist air from the tub and shower did not get circulated enough and mold/mildew became evenly visible on the 3’ x 6’ ceiling. So, I added a timer to the exhaust vent to run 15 minutes every six hours which has solved the problem.

well Dave, I see that the contractor posted his findings so I wouldn't worry too much about upsetting or offending anyone. it isn't unusual for there to be conflicting opinions, but the fact is that you and he are the only ones who have seen the ductwork. his discription of your return air setup is suspect. I see he is advising you to wait out the summer to do any duct/return modifications. if you can, do. it is awfully hot to be modifying ductwork this time of year. a rushed job isn't a good job. better someone take the time to properly install and seal ducts. it kinda bothered me that no mention of duct or return sealing was mentioned. of course the discussion is pretty technical. but I find that leaky ducts/returns are often overlooked. when you talk about the kids rooms and the 3-4 temp difference, you mention west facing windows. how many & what approx size are in each room? what type of windows do you have? single pane, double pane? metal frames, vinyl frames? clear glass or low-e glass? if the temp difference is due to the west windows..and it would be here in my area, then there are a couple of things you could try. block the afternoon sun from the exterior for a day or two and see if this evens out the 3-4 degree temp difference. wouldn't have to look great, or be permanent, just stop the solar gain. if you can keep the heat from entering the house, then the a/c doesn't have the added load to temper. exterior shading is the best route. rather than interior shades & curtains. beat the heat before it gets inside. if this works then invest in solar screens. yes they are darker than normal screens, but they will minimize heat gain. if windows are double paned..you can't install window tints as it will increase heat between panes and blow the seal. awnings and bahama shutters are other options but to me..at this point solar screens would be more cost effective. right now you have more time than solutions, so give it a try. don't worry about riling those guys up..they live for that stuff. Shophound & the guys have a good handle on things, so let them talk themselves around. I have to admire your restraint & patience. you are aware that 1" pleated filters are very restrictive? for now I'd change to a less restrictive filter. at least then more air will return to the unit. hang in there. best of luck.

I've never seen supply vent in hallway in your 1400 sq ft one story home in florida what size unit was installed? what was the size of the one that was 'far too small' that was replaced. are you aware that bigger is not better? did the company who upsized the unit tell you that your ducts would be too small for the larger unit you had installed? this is probably why another hvac company mentioned changing ductwork. by 'one step higher than specs called for' do you mean that you put 14 SEER instead of industry minimum of 13 SEER? where are your ducts located that they condensate? vented attic? crawlspace? or is there some other meaning to this statement? you could try a stand alone dehumidifier to remove humidity. larger unit may have short cycles that prevent it from running long enough to dehumidify. long run times are not a bad thing in a hot humid climate. utility companies don't troubleshoot for hvac. they may shoot a couple of temps but they don't know hvac. best of luck.

With a santee and an AV vent.