Hi all i'm back. look at http://www.digchip.com/datasheets/parts/datasheet/477/TPS53355-pdf.php

its the data on the tps53355. look at fig 17,18,19,20  shows a about a 3% inceras lowering the voltage but only in the 4-6 amp range. + or - lowers efficiency. also the lower the out put voltage lower the efficiency.

so this chip is at best 90% with a 90% psu so give the power co. 19% of you btc on a good day. if i have to take a stab at it i would have to say 75% makes it to the asic.

the further you under volt the less the PSU efficiency. with the increase in hash rate and lesser efficiency it may be brake even or worse.

i say we need to look else ware. fans at 100% X2 is about 25watts on a 90% psu is a 4 watt loss per miner.
go AC fans or one big one.

im looking at solar. roi in 4years and if this BTC thing is a bust can sell KWHs back to the power co and 90% efficiency.also standard solar pannals can be configured as 12v or 6v.

fyi the asic blade will continue to work at the lowest 4v and the control board will cut out at 5V.

hope it helps.