Which implementation of Scheme? Gambit has Termite, but lacks a good standard library, whereas Chicken is the other way around.
It's having to make decisions like these that make me nervous about learning a new language, and long for good old safe-but-boring Java. At least there's only one (for now).
A problem with LISP ((aside(from)()()))all (the()()(damned))))brackets))) is that the established LISP "gurus" have got so tired telling everybody that there has been nothing new in Computer Science since 1954, that they have become bitter, twisted and vindictive:
You need to consider more than just the server limit though - what about all the proxies, gateways etc that the request might pass through? Any of those could either crash or truncate a long GET request.
It's probably be safest to keep within the IE limit of 2048 bytes, since most things will be coded with that in mind.