I've not done it personally, but have read of many who have saved lipo that way. Have seen typically 1amp used, charging as a NiMh only until voltage is back over minimum, 12v, stopping NimH charge and the starting a proper lipo charger sequence.

If lipo is pretty new and it has not puffed, prob will be pretty normal to use. If its older, pay attention when running and charging -may puff. Cell quality is diff it seems, better quality seems to tolerate overdischarge better than poorer quality cells.