Have you cleaned the A/C stuff lately, fins and those sponge filter thingys???
We usually turn on the ceiling fan when we run the A/C, helps spread the cool air around.
Something that has really helped us FEEL more comfy is to change out those ceiling vents. SteveR (I think it was Steve) pointed out that you could change them out getting some from a Jayco dealer that spin in and out. Al changed out 4 of our 5. The one in front of the shower, he actually left the old one on, but the one over the bed and the 3 in our main living area he changed to the spinners. The one over the bed is totally closed off, the other three are totally open. Wow, what a difference back in the back by my desk!
Course, if you have the DUMP open on the A/C, then the positions or types of the ceiling vents don't make a whole lot of difference.
On really hot days like you are experiencing, we pull the day shades and the night shades all the way down, makes considerable difference. And, on really hot days, we have stuffed pillows up in the vents we can reach, and actually figured out a way to get a bed pillow up in the shower sky light. The pillows also made a noticeable difference. You can buy stuff for that at CW, etc. But, we are only gonna use a couple of times a year, so we are saving that cash, spending it on fuel, and stuff the pillows up there when they are needed.
We rarely have days that hot, just 4 or 5 a year. And, this year, those were all in the RGV in March. So, we don't feel we need the 2nd air, BUT, if we were going to spend a LOT of time in warmer climes during the summer months, then we would love to have the second A/C.