The roll whip does give you a tight middle and floppy sides. The tie outs take up the slack in the sides and help spread the hammock out. I, personally like the tight middle as it supports my back and helps me to get flat.
It seems the roll whip takes a little tweaking to get right. HE was having a problem getting it adjusted right. May not be for everybody.
“Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it."