Yes, that spec seems somewhat elusive. First, I would try to get support from your fork manufacturer. It is, after all, their steerer tube you are putting the squeeze on. It's probably intentional that Ritchey does not include that spec as you could be using anyone's fork. You need not think too far out to see that this spec could be a liability in the case of an accident caused by steerer tube failure. It's sad, but true ;-(
While I am a proponent of the use of torque wrenches for CF components, I have done a little experimenting and found that if you tighten things down to the point where the component stops slipping you will not (in any case I have tested) exceed any suggested manufacturers specs. This is pretty much the method that Sheldon Brown advocates. So, for the steerer tube binder bolts you'd straddle the front wheel between your legs and tighten (just a little at a time) until the handlebars no longer slip around the steerer tube. For the curious, you can do the incremental tightening with a torque wrench and see where you end up at.
The big problem with CF components seems to be the person that just tightens fasteners for the sake of tightenning them (i.e. they go over the whole bike and put an additional quarter turn, or whatever, on every single fastener). If you feel the need for re-torquing, then loosen first and then torque down. Repeated, additional tightening is what will eventually crack CF tubes.
It really takes an incredible amount of force to crack a CF tube. If you just "tighten until it stops slipping", you will be just fine. I forget where I read it, but I saw a tip that said to tighten your hand controls until they just stop slipping on the handlebar. This way - if you crash - your expensive Shimano STI or Campy Ergo brifters have a chance of slipping around the bar, as opposed to snapping off.
