When asking for technical help at the very least let us know the version of firmware you are running.Cliff's Calibration (Mapping) Guide is a MUST READ: http://www.vemssupport.com/forum/index.php/topic,97.0.html
Oh, sorry, my fault. Power flyback is just for Low-Z. And works bad.Instead of power flyback you need just such diode:http://uk.farnell.com/fairchild-semiconductor/1-5ke30a/diode-tvs-30v-1500w-axl-unidirc/dp/1700782