I've found that trying to fit an Orion Lipo into an M03 makes the battery end plates bend out so it doesn't really hold it securely.
After seeing a Japanese article on the M03R showing some tips on how to make a 4200 fit better, I realised the same would also work for a lipo.
You just need to cut the end plates as shown and the lipo will fit perfectly. Hope this helps some people, lipo's really are a great technology, myself and my friends have had so many IB 4200 cells die or drop voltage with 1 or 2 month old packs, a few of us have been using lipos now for 8 -9 months with no problems at all.