Maybe i'll get kick ass for this, but i try.
I suggest you to test max bitrate what gh2 can handle, with this way.

1. Get the fastest sd-card wich present at this moment.

2. Make firmware.
In ptool enter this settigs
E1 Quality=200
E1 Table=4
E2 Quality=200
E2 Table=4
E3 Quality=200
E3 Table=4
E4 Quality=200
E4 Table=4

3. Shoot
Of course choose on your camera 720p MJPEG mode.
Then try to shoot, if record time is > 15 sec, that mean it's ok (this is my guess), note what bitrate you have got
Shoot every time same scene!

After, enter this settings (Every Quality setting is higher by 100)
E1 Quality=300
E1 Table=4
E2 Quality=300
E2 Table=4
E3 Quality=300
E3 Table=4
E4 Quality=300
E4 Table=4
Try to shoot, if record time is > 15 sec, it's ok, note what bitrate you have got

Repeat this until the errors start to happen, after you should take last successful settings, and start new tests, but now you should test with litle steps, let plus every Quality settings in every step by 10, for exemple:
You have got successful settings
E1 Quality=600
E1 Table=4
E2 Quality=600
E2 Table=4
E3 Quality=600
E3 Table=4
E4 Quality=600
E4 Table=4
And you further actions:
E1 Quality=610
E1 Table=4
E2 Quality=610
E2 Table=4
E3 Quality=610
E3 Table=4
E4 Quality=610
E4 Table=4
Do it untill the errors start to happen

Shoot every time same scene!