There was a thread a while back where quite rightly Andy H raised some questions as to the correct way to adjust the steering box. Iirc the suggestion was that the box had to be removed from the car going by some other models, in order to do the job correctly.
Well, during discussion with these guys,
http://www.steering-racks.co.uk regarding fiddling around within steering racks and conversions from steering boxs, the subject of box adjustment came up.
Suffice to say there is only one adjustment, the torx screw and lock nut on the top as we know, and there is no reason to remove the box from the car to adjust it. With front wheels unloaded, lock nut undone, they confirmed that, with an assistant moving the sterring wheel back and forth gently, the torx nut can be slowly tightened until movement can be felt on the torx nut.
It IS a question of feel and they confirmed they've done loads the same way, including repairs to omega units involving a full strip down.
So, just to confirm, adjusting the omega steering box is no problem at all. Providing its adjusted correctly of course