problem with optiflasher

i recently backed up my firmware for E710 using optiflasher, it took about 25 minutes and the resulting filesize was about 49Mb, i want to upload another firmware to this phone to remove the vodafone branding, the firmware i have is only 11Mb, and when i press flash it does the whole process in 39 seconds and then says job finished.

when i switch the phone back on after removing/replacing the battery the phone switches on still with vodafone crap on it, i know i'm doing something wrong, could somebody please throw some light on the situation.

thanx in advance