When the control horn attachment points are NOT the same distance apart as the driver (tiller bar or servo arm), the control surface will tend to NOT return all the way to center every time. Each time it will be off slightly, generally in the direction it was last moved. The difference between those distances is mostly what contributes to slack cables on the unloaded side. Do some significant reading in the IMACC and pattern forums and you will find pages and pages of threads about that and MOST consider it to be a problem. I did not understand that some folks seem to enjoy control surfaces hunting while most of us prefer more precise operations, but to each his or her own.

I have seen some with control surface lines that were loose enough to almost drape between the servo and the control horn and on some aircraft they seem to work, but most of the folks I fly with prefer taut cables when at neutral and we generally work hard to keep the cables reasonably tight throughout the control surface movement range. Getting the cables too tight will not correct a sag problem if you have a 1/2 inch servo arm and a 1 inch control horn. Flutter in rider scale birds is (mostly) a function of speed and the CG of the control surface being behind the hinge line (and they DO balance them after painting), but in models it generally comes from speed and soft control 'rods' which is what you have when a cable is sagging when not under load.

I prefer direct connect, but CG issues rule almost all of my installations because I really really REALLY HATE adding extra weight to get it right.

Cheers!