glad you thoght training wasn't 100% waste of time and total disaster. Never planned a training like that for anyone (has anyone done such corridor ever?), so hard to tell in advance. There is theory why it might be good training in theory, but thats just theory.
I have never seen an inverted corridor before. It's a good idea, keeps you focused ahead, looking up. The difficulty level will depend a lot on the terrain. With less detail a compass would be v useful.
I've never seen a training like that either... very interesting!
I couldn't help thinking about how I would do it. One obvious thing to look for are linear any features which cross the corridor; also, big obvious features that are a bit ahead and to the sides. As Neil said, that would keep one thinking ahead and force one to look up. That would probably help to tease one away from relying excessively on the technique (habit) of stone/knoll/other-small-feature hopping... and help to remind one that other techniques can be more useful.
Feature-hopping is something I'm prone to doing. At a training just the other day I suddenly realised that in getting to a control by engrossing myself in the details, I had completely missed the big catching feature just a little behind it.