You should ask the Icecap folks. Check this out, too:
http://www.reefgeek.com/lighting/T5_Fluorescent/IceCap/SLR_Retrofit_Kits/48_inch__2x54W_SLR_T5_Very_High-Output_Retrofit_Kit_w!_Bulbs_by_IceCap
"IceCap ballast engineered to "over-drive" each bulb to approximately 85 watts for superior...