I noticed no difference in the hang if everything was somewhat tight. The only time I did notice a difference was when hanging between trees too close and the ridge line between the butterfly loops loosened. If it did change, it was not enough that I could tell a difference in the way the hammock hung. In my experience with the SLS, whoopies at the hammock are not needed unless, you don't want to tie/untie the butterfly loops to get your first initial setting correct. Olddog did this with his system, he used whoopies to make the initial setting the way he wanted it allot easier.
You can achieve the idea of the SLS system with a normal suspension system. Set it up tight with the ridge line of your hammock tight. Get in and see how it feels making sure the ridge line is tight when your in the hammock. Now tighten up the suspension more or loosen it a little making sure the hammocks ridge line is still tight. Your hang will be the same because the hammocks ridge line is preventing the sag of the hammock from changing, because its pulled out to its maximum length. The hammock is just going to hang down from that max length. You can string that hammock up between the trees as tight as you want, banjo tight if you wish. But you will see the hammock still just hangs there exactly the same. Now loosen the system up until the ridge line of the hammock is loose and try it out, it changes. That's because your hammock is now taking on the same angle as your tree straps coming down.