I can *almost* follow this paper talking about passive snubbers:
http://www.ee.bgu.ac.il/~pel/pdf-files/smnr13.pdf plus some ltspice nomenclature included.
edit: this does not lend itself to a half bridge igbt boost unfortunately (assuming using top body diode). Not sure what bi-directional boost/buck would look like either, it might snap together though back into a half bridge with additional diodes.