[plt-scheme] Has anyone written a tabular or grid editor%?

Hi everyone,

Just wondering: has anyone already written an pasteboard editor that 
handles tabular or grid layout? I see MrLib's aligned-pasteboard<%>, and 
composing horzontal-pasteboard% and vertical-pasteboard% almost works, 
except that my cells aren't guaranteed to be the same size.

Before I go out to implement one, I just want to make sure I'm not 
duplicating effort.  Thanks!