Deb
I find 20-40 to be an intolerable pressure and unless there is some question of the ability of the pump to handle the higher pressure, I believe that 30-50 is the lowest pressure you can take a half-way decent shower with and 40/60 is better. I have a 40-60 on my system.
I think that it is a good idea to either check that the pressure the gauge is reading is correct or install a new gauge. The air in the tank should be 2lbs less than the kick on pressure for the pump and adjusted when the tank is completely drained of water. So put the air pressure in the tank to correspond to the kick on pressure you want to end up with, connect a hose to the drain at the pressure tank, adjust the pressure switch, open the drain to run water and note the pressure that the pump kicks on, adjust, drain, and check kick on pressure until it is 2 lbs over what you put in the tank. There is also no set run that you need to adjust to 30/50 or 40/60--you could have 35/55--it is just recommended that you maintain a 20 lb differential between on and off.
Deb
The Pipewench