[plt-scheme] Hashtables and case sensitivity

I have what I hope is a simple question. I've noticed that in Pretty
Big, 'x and 'X are not treated as the same (though they are in R5RS).
It may be academic in a sense, because hashtables are not a part of
R5RS, but in the interpreter I'm working on, I chose to use hashtables
instead of association lists to manage the symbol table, and eventually
I'd like to use be able to use case sensitive identifier names. I
started to use strings instead of symbols for my hash keys but later
decided this might not be a good idea and so I'm using symbols (the
default). Anyway...my question is just this: Is this safe? If I want x
and X to be different, can (should) I use 'x and 'X, as keys, or do I
need to use "x" and "X"? 

===
Gregory Woodhouse  <gregory.woodhouse at sbcglobal.net>
"All truth passes through three stages: First, it is ridiculed.
Second, it is violently opposed. Third, it is accepted as
being self-evident."
--Arthur Schopenhauer