The target goes down or not. That's all that needs to happen as far as the players are worried about. Any detailed info is needless chrome that muddies the waters and slows down the game. In fact, in over 3 decades of running and playing the game I've never had anyone worry about such things.
Ditto.
I often describe my 'rational' for unusual roll targets, allowing Players to remind me of any forgotten aspects. Like a prior injury, a skill, background or recent roleplay I forgot. The latter is extremely rare, given how concisely a CT PC is defined by just a handful of skills.
My players don't really worry about mechanics - that's my job. Its also my job to make sure they don't have reason to worry about the mechanics...
... So when a PC shoots at an NPC (or another PC) wearing combat armor and rolls a hit, what do you (as a ref) do next in that situation as far as damage/injury?
If the adjusted target roll is met on the 'to hit' roll, then an attack has penetrated the opponent's combat armor (i.e. - it is an effective hit). Roll for damage and apply as appropriate.
My take on characteristic relationships is different from Mike's, but the essential concept is the same. In my games, DEX, for example, often involves joints - relative amount and roleplay determines where and to what extent, ex: spranged vs. broken wrists; cut thumb vs. dislocated; etc. END can involve blurred vision and concussion which is more roleplay elaborated - but can affect NPC actions 'mechanically'. The rules provide for END to limit effectiveness via 'weakened blows', for instance.
If the 'to hit' fails due to the range of the combat armor DM - then I will often describe some 'damage' to the combat armor. Depending on the nature of the attack, actual roll and roleplay, such 'damage' may result in changing the DMs or impairing the owner in future actions.
Failing a 'to hit' just means no effective hit - glancing blows, cloth snagging munitions, hair searing lasers, etc. can still be described for close rolls.
Upon exposure to the unified task mechanic and expanded skill aspects of MgT, I thought - wow, this is great stuff. It seems like CT should be harder because it defines less for the Ref. But then, after playing and trying to codify what I had been doing with CT for decades, I came to the realization that a number of others seem to share... CT's simple and vague rules, and less expansive chargen, have some really nice inherent properties.
Either ruleset, and probably most, can be
made to work - but, for myself, the effort with CT is minimal. Maybe I'm forgetting difficulties, but I don't think so. I remember flipping through the books in the first two or three games - but since then everything just seemed natural. A handful of pages for table reference, some pre-genned NPCs and worlds, and I'm good to go... heck, given familiarity with UPPs, skills and UWPs, one can wind everything.<shrug>