[querty1000]

Code:

avoid_pwm_pll=1
h264_freq_min=333
over_voltage_min=1
arm_freq=1000
core_freq=500
v3d_freq=333
sdram_freq=500
over_voltage=2

If that is unreliable, remove the sdram_freq setting or increase the over_voltage to 4. If it is reliable you could try increasing arm_freq to 1100.

sdram_freq=500 was on three different PI's too high, better using sfram_freq=480. I have never tried "over_voltage_sdram=x", maybe this helps.