I made a few comments about structural ridgelines a few days ago in another thread. I think those comments are appropriate for this discussion so I'll repost them here.
I have noticed that adding a structural ridgeline is a popular thing on this forum and have often wondered if people realize what the fundamental tradeoffs are. The way I see it is that a structural ridgeline allows you to achieve a consistent sag angle for the hammock as long as the angle of the hammock suspension lines is less than the hammock sag angle (without a structural ridgeline the hammock sag angle and the angle of the suspension lines are the same) and it therefore allows, or even encourages you to tie lower on the trees.
The tradeoff with that is that the forces on the hammock suspension line increase when the angle on the hammock suspension lines is made smaller. By lowering how high you attach your hammock on the supports with a structural ridgeline you are decreasing the angle of the hammock suspension lines and applying more force on the suspension lines. You need stronger suspension lines and should use more care for attaching to trees when you use a structural ridgeline.
But even with that you are still applying more force than you would without a structural ridgeline and more force is not a good thing. The question as to how much force we are talking about is not one that can be answered without putting boundary's on things because the math involved allows a solution without bounds and in practice there will be some boundary's because something will stretch or fail or you would never try to hang the hammock that low.
For what it is worth, my rough guess as to how much extra force you are talking about would be that the enlightened hanger that makes a reasonable attempt to hang high would put less than 2x as much force on the suspension lines by using a structural ridgeline. Those that don't might put as much as 3x or more force on the suspension lines.
Of course if you wanted to be ultra enlightened you could hang it as high as you would if it didn't have a structural ridgeline.