[Haskell-cafe] how do I pass customization items in syb code?

I'm looking at the XML SYB example http://www.cs.vu.nl/boilerplate/testsuite/xmlish/Main.hs I'd like to find a way to pass other type customizations as arguments to data2content and content2data. I modified data2Content as follows: data2content f = element `ext1Q` list `extQ` string `extQ` f But I can't figure out how to give f a type such that (data2Content $ myFooElem `extQ` myBarElem) operates on both Foo and Bar elements. Right now I am giving f the type f::(a->[Content]) which compiles but causes the wrong behavior. Any recommendations on how to fix this? -Alex-