I think it's important to point something out; something intimated but not said directly. Forgive me if I'm stating the obvious.
There is more to switching from high to low pressure than changing the orifice. In order to have a low pressure system you need a low pressure supply. Low pressure LP runs at 11" water column, or a little less than 1/2PSI. 10 PSI is considered high pressure, so right now you're running a high pressure supply through a low pressure orifice. if your regulator is adjustable, you might be able to crank it down far enough to get an acceptable pressure, but you'd be better off getting a proper low pressure reglator. That, or switch to high pressure orifices.