With help from MJ, got the isetools.jar validation working for my output, and clarified a few things with MT relating to warnings from it (bad nesting is perfectly OK, although the jar warns about it). Turned my transform into a two-stage process, so I can post-process the results to clean up some whitespace issues (and there will be other things); added support for <MODE> (not fully tested yet because my sample text has no transitions); and imported some more content into my schema from Simple.