Large, meaning how large? One story, two story, basement, finished? Just one furnace/ac? what type?

I think they should put two units in large houses with multiple floors. Works so much better than one. Plus if one conks out, you've still got one working.

Do you know the size and type of AC/blower?

My first question would be is the unit large enough. Several related questions depending on various stuff. Maybe you should have the HVAC provider out to run thru the unit size, installation and use with you. Also if the unit is working properly. You should get more out of that than asking for people to guess.

If it's just not sized right for the house, it's not sized right.

Blinds should help but obviously you don't have them so have to find other ways to cool the house. Have you tried cooling the house down as much as possible at night?