What I do is keep some cheap 2GB SD cards with different hacks on them so I can switch it out for different situations. Most of the time I use Cake. Its completely reliable and the bit rates I believe are 66mbps in 24p and 44mbps in 60p. When I don't have to worry so much about reliability or card space, I use Quantum X, which is 100-154mbps I-frames. The quality is ridiculous but it doesn't play back in camera and a 16GB card holds like 4 min of footage.
Quantum X and a lot of other good patches: