If you don't use the 20 PSI differential you won't have 25 gallons of drawdown in that tank. With a 50/60 pressure switch the tank would only deliver 12 gallons of water. So there is no problem keeping the switch at 40/60. You just need to set the CSV at about 58 PSI so it doesn't tank too long to fill the pressure tank. That way the CSV will not do anything until the tank has refilled to 58 PSI, then the CSV will keep the pressure constant at 58 PSI for as long as you are using water. Then when you shut off the faucets it will only take about 2 minutes for the CSV to fill the tank from 58 to 60 PSI so the switch can shut the pump off.
I have plenty of those digital pressure switches for 30 bucks if you want one. But digital pressure switches suck, which is why mine are discontinued. They have re-engineered those Guardian ones about 3-4 times already, so maybe they are a bit better, but they will never be as dependable, long lasting, and inexpensive as the regular 40/60 mechanical switches.