If they are so different in weight, GSP's camp wouldn't even have suggested Silva drop down to 170 then?
Pretty sure Silva said he might go down to 170 for the fight.
Once again, I reiterate that I have no interest in seeing this fight. I admit, Silva is the bigger man. However, the size difference is definitely not as big as everyone think it is. If the fight happened at catchweight of 178, I'm pretty sure Silva would only be about 8~10 pounds heavier than GSP on fight night.
Silva at 205, UFC 101: