as a fan of big screens using note 4 , iPhone 6SP and Sony Xperia ultra. One hand use is no problem if you have the proper tools. Gestures. As an heavy browser man Dolphin is the way to go. You can create gestures and assign tasks.

Have fairly big hands so that might affect too, ofc top of the screen is not easy to it without tilt/refreash grip on the ultra.

But then again most software is not designed for big screens with buttons in the top. Browser url field in the top and so forth...ui designers got a lot to learn

Sailfish got a few great things like the pullymenues but too limited .what they should really do is user designed gestures for the OS. That would elevate the OS to something unique.

And split screen atleast for mail and messages at start . It's a must on big screens