I have a very small tank (4 gallon draw down) on my 25 GPM 2HP pump. That is because I hate the low pressure I get in the shower, as the tank is draining from 70 to 50 PSI. Once the pump comes on at 50 and the system quickly builds to 60 where the CSV holds the pressure constant, the pressure in the shower is tremendously better. So with a small tank, I get constant pressure in the shower very quickly. With a large tank, the pressure in the shower is low and continues to get lower for the first half of my shower. As soon as the pump comes on and the CSV is maintaining a constant pressure, the shower pressure is great. People who have experienced this and now have a CSV on their well, tell me that the pressure is so strong, they don't even need soap in the shower any longer. The constant pressure from the CSV just blast the dirt off, so no soap is needed.
I was going to mention that you should be using an expansion tank after a pressure reducer on the house line. This is not for thermal expansion, as the pressure reducing valve should have a thermal expansion by-pass. The expansion tank is to absorb "creep" from the pressure reducing valve. Without an expansion tank, a "creep" of only 1 teaspoon of water would cause very high pressure on the house side of the PRV. An expansion tank is just another component you have to add when using a PRV to control house pressure. And if the PRV does hold the house pressure constant on the house, then the water in the expansion tank will get stale and contaminated. Then when the water is turned off to the house for any reason, the contaminated water in the expansion tank is expressed into the house lines, contaminating everything. Creep on a PRV does happen, you just haven't seen it because of the added expansion tank. There are really only two kinds of valves ever made, those that leak or "creep", and those that will leak or "creep".
I don't understand why anyone would want a system that needs to be engineered precisely, balanced perfectly, and then used very carefully, to prevent destroying the pump system. Adding a CSV means the system can be used anyway you want without worrying about it. A CSV controlled system is even less expensive, as it can utilize a much smaller pressure tank.
I can see where engineers and irrigation contractors might be concerned about their job security as the CSV eliminates the need for "engineering" and "balancing" perfectly. The CSV can make water systems do some incredible things. Those who learn what the CSV can do, are designing systems that are years ahead of their competitors. Engineers and irrigators who continually try to design around a CSV, are not using the latest technology available to enhance their system designs.