If you want to add a regulator in between your house supply and the generator, you may have a problem that could be hard to rectify. Gas pressure regulators require a minimum differential pressure across them to work properly. Regulating pressure from 11"WC to 7"WC does not provide much differential for the regulator to function properly.
I strongly suspect that the pressure supplied to your meter is in the range of 2 PSI (about 50"WC) and the regulator after your meter then controls the 11"WC pressure being delivered to your house and generator.
I can think of two solutions, but the first depends on the gas appliances in your home.[LIST=1]
[*]If [U]all[/U] of the appliances in the home can use a lower pressure (7"WC) AND if the piping sizing is suitable for 7"WC delivery pressure, the gas regulator after your meter could simply be backed off to deliver 7"WC pressure. This assumes that the currently installed regulator is sized to handle the total load of all appliances in the home and the generator.
[*]If the appliances need a higher pressure than 7"WC and/or if the piping sizing in the house would not be quite suitable for a lower pressure than the 11"WC you are running, then a second regulator could be installed between the meter and the currently installed regulator. The new regulator would be smaller than the main one, as it would have to deliver only 156 cubic feet per hour (the 100% load rating for your generator's engine) and would not have to supply the pressure for the house.[/LIST]It's obvious that you need somebody qualified to help with the gas delivery system engineering to analyze your situation more closely and help specify the solution for you.
One thing that's critical is that the meter and regulator(s) are properly sized for the loads they must deliver. I had to have a new meter and regulator installed to feed my home and generator when installing the generator, as the generator alone would have nearly maxed out my old meter's delivery capability.
Skip, I have no regulator before or after my meter since I am in a low pressure area according to the gas company technician. I am getting bids on installing a regulator on the gas line that feeds the generator. The pressure at the water heater is more like 12.5 inches or 7.25 oz. My stove and water heater can take from 5" to 14".