I've run a DualCross with 6 volts packs for an overnight canoe race without any problems. Another time I ran 4S Energizer lithium AA battery pack, about 6.5 volts, for several hours, again without any problems, on a DualCross with Cree Q5's in it. Temperatures were cool, so I don't know if it would work ok in warmer weather.
So, it worked ok for me.
Yaz