Hi, I run these lipo's in my df03:
http://cgi.ebay.co.uk/RCS-4100mAh-7-...item45f5ebb580
I had to file about 5mm on the chassis to get the connectors to fit. Besides that they fit perfect and they really good batteries. Had them for over a year now and they still 100%.
They also make a 5200mah one with slightly different measurements:
http://cgi.ebay.co.uk/RCS-5200mAh-7-...item3f03dd9dda
Not sure about runtime though. I ran for about 15 to 20min with the 4100. I was running a brushed system though and I was running the lipo down to 6.6v.
Hope that helps mate. I can take some pics of the car and lipo fitted and the small bit I had to file away if you want. Pretty easy to do though. Ones you put the lipo in the car you will see exactly what I mean.
Let us no how you get on.