Does the displayed range read out change at all with the Y cable installed? Curious to see what happens with 2 batteries.
From my experience with the paralleler, the battery range is still just for a single battery. I think this is because it is just a calculated value based on the battery voltage.
It does go down slower, of course, and you can work out the total range by adding the values for each battery together.
With the paralleler installed, I don't really look at the range anymore, I even changed the display to temperature only, as range is not as big an issue now.