Set your thermostat to a temperature that is comfortable to you in the RV.
75 degrees is a good start… You cannot “trick” the A/C unit into cooling differently. If your A/C system is not cooling the RV, you can do a few things…
1. Clean the filter(s)
2. While the filter is off, look at the coils/fins. If they are iced up, one of two things is happening… Either the coils are dirty and not enough air is going through the coils so thae are freezing up. Get some A/C cleaner and clean them off. If they are clean and iced up, you have a refrigerant leak. In this case, you will likely need a new unit. Most RV A/C units are not chargeable/repairable.
2 A/C units should cool the RV to 75 degrees without a problem. I had my 34 ft Class A running on one A/C with outside temps over 100 degrees, the RV in full sun, in Florida, in July and kept the interior below 80 degrees the entire time. (The BR A/C took a dump mid trip)