I do not know why it overflows. It's been a while, but isn't the answer usually "too much laziness"? Maybe try changing the foldr in fromList to foldr'? I would try it out quickly but do not have ghc installed on any computers here.
I am happy start a repo for this library, but there is not much history to import so anyone else may do it. I'm not sure how hackage upload permissions work... I guess I just change the maintainer field in the .cabal file from myself to someone else...? Any volunteers?