I have the Nomad with an Aluminum eccentric that is held in place by two bolts that have conical pointed ends that dig into the Aluminum to hold it in place. If your bike uses the same type of eccentric for adjustment that mine does, you have to be careful that you do not adjust it too often.
Each time you tighten the bolts to hold the eccentric, it makes new small depressions. You do not want the depressions to be too close to each other, otherwise you could eventually end up with two long grooves instead of a series of depressions. Instead, later when you use replacement chains you will be re-using the same depressions you previously used.
I can't say what the optimum distance apart for the depressions is, maybe others will comment?
After you adjust the chain, turn the crank backwards by hand for several revolutions to make sure that the chain does not bind too tightly at any one spot. If your chainrings are not perfectly concentric with the center of the bottom bracket, you could have a tight spot on each crank revolution.
I have never measured the amount of slack, I just do it by feel and I make sure that after I am done adjusting it that I can easily turn the crank without seeing or feeling any chain binding.
On a couple of occasions I found that one of my bolts had loosened up. Thus, I now put a couple rubber bands on my bolts so that they can not vibrate and fall out if one gets a bit loose. I am sure I initially had my bolts tight, but when you pedal you put enourmous pressure on the bottom bracket and ecentric and I suspect that my weight and pedaling effort pushed the Aluminum a bit farther into the conical ends of the bolts which allowed them to loosen.
