I like to mount the battery on the bottom of the quad. This places the battery close to the center of gravity. There are already cutouts in the bottom plate for Velcro battery straps. The only problem is that the battery can slide forward or backward in the strap and eventually fall out.
To stop the battery from moving I have made the most minimalist battery holder I can think of. On a mini quad the weight is paramount. Every gram counts The mount consists of two brackets that are mounted on both sides of the battery and hold it in place. No modification of the frame is necessary. Neither is it necessary to replace any hardware (nuts and bolts) since the original bolts are long enough to hold the brackets.
I use Nanotech 1300 batteries and the holders fit perfectly for these. But many 1300-1500 batteries are the same size and will fit.