Is the 6" pressure regulator suitable for 12" pipe line?

We had a challenge to find the best valve that we have in the shop for the data sheet below

The first step checking the Cv?:

Now it's time to go to the FISHER products that we have in our shop which is suitable for calculated and rated Cv

Type LR125 Pressure Reducing Liquid Regulator

The point is maximum regulator size for LR125 is 4"

Table 7. Flow and Sizing Coefficients for Type LR125 Main Valve at 100% Capacity

The Cv for both scenario is 147 and 151

The Cv for 4.5 bar output pressure is between 129.6 to 147 and the allowable pressure drop from 10 to 40 percent. The point is calculated Cv is 90.366 and it shows 6" pressure regulator is acceptable.

According o the table 12 , page 10 the flow rate is between 3293 to 6409 L/min or 198 to 348 M3/hr and it shows LR125 size 4" is ok for 12" pipe line

For more checking we have another regulator Manufacturer: BERMAD waterworks series 800 The last page of the catalog

For choosing the best valve size, calculating the Cv and checking pressure drop are the most important steps and after that checking pipe tension in the line.

Some time using small size valves with reducing pipe adaptors is better than use large size valves with small amount of Cv?