I'll have to look at mine, but if they are what you are describing, it sounds like you might need some sort of spanner wrench.

 

I'm not really sure on the convertibles, maybe someone who has a convertible can help you. Sorry.

 

"some sort of spanner wrench".

Exactly!

 

If your C4 is not a convertible, the "nuts" you are referring to hold the glass to the hinge assembly and you surely don't want to take those loose. There are 2 torx head bolts a little bit more inboard that hold the light assembly to the hinge assembly, at least that is the way it is on my 86.

 

Aha! You are so right! Upon even closer inspection, I found the two Torx Nuts you describe. My hatch doesn't seem to go up high enough to actually get the ratchet AND the torx socket on there however. Does one need to disconnect the hatch for more access?

 

I would take the gas lifts loose, but support the glass well, because that back glass is VERY expensive and VERY hard to find. Then you might be able to lift it up enough. What you might be able to do is, if your sockets have removeable inserts, take the torx insert out and use it with a 1/4" open end wrench on the insert to break the screws loose. Good Luck.