if you move your cfls about 3" away you would get better resolts as well . lets say your cfl puts out 1750 lumes thats at 1 ft so if you move your cfl to 3" you will get 5250 lumes and a lot less heat then you would with a hps . here is a nice guide i found online hope it helps
HID Lighting Helpful Tips
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Hanging height: Due to the heat that is emitted from these types of fixtures, you should hang them according to size. Smaller wattage systems (100 and 250) should be hung about 2 to 3 feet from the top of the plants. Medium wattage systems (400 and 600) should be hung around 4 feet from the top of the plants. High wattage systems (1000 and up) should be placed at least 4 to 6 feet from the plant tops.
<TABLE cellSpacing=0 cellPadding=3 width=600 align=center border=0><TBODY><TR><TD width="33%">
HID Light Output
</TD><TD width="33%">
Primary Growing Area
</TD><TD width="33%"><CENTER>
Supplemental Growing Area </CENTER></TD></TR><TR><TD width="33%">
100 watts
</TD><TD width="33%">
2' x 2'
</TD><TD width="33%"><CENTER>3' x 3' </CENTER></TD></TR><TR><TD width="33%">
250 watts
</TD><TD width="33%">
3' x 3'
</TD><TD width="33%"><CENTER>5' x 5' </CENTER></TD></TR><TR><TD width="33%">
400 watts
</TD><TD width="33%">
5' x 5'
</TD><TD width="33%"><CENTER>8' x 8' </CENTER></TD></TR><TR><TD width="33%">
600 watts
</TD><TD width="33%">
6' x 6'
</TD><TD width="33%"><CENTER>10' x 10' </CENTER></TD></TR><TR><TD width="33%"><CENTER>1000 watts </CENTER></TD><TD width="33%"><CENTER>8' x 8' </CENTER></TD><TD width="33%"><CENTER>12' x 12' </CENTER></TD></TR></TBODY></TABLE>