The Extend-a-flow, extend-a-stay and stay-a-while all go between the tank and regulator and deliver roughly 100 PSI to the grill, thus you need a regulator at the grill.
Some folks tap the low pressure line post regulator, This is how many trailers with "optional grill" are set up at the factory.
I prefer the first method (High pressure to grill) because I have options.
If you modify your grill by removal of regulator, You can kiss those last two options by by.
Also, on a motor home with a mounted (Bolted on) tank instead of a trailer with a removable tank, The last two devices above (Stay-a-while and extend-a-stay) give me the option of using an external tank to charge the RV's propane system.. Handy when the big tank hits "E".
Home is where I park it!