The shermans final drive is placed in the front portion of the vehicle, and has a rounded shape, yet i have hit low on that front armor and watched rounds bounce...this seems unlikly, the same goes for the turret, round is a shape particularly bad for deflecting rounds as there is always a flat surface facing the incoming round.
And as for the firefly being up armored, accept for a couple patches over the ammunition boxes on the sides ( building of armored boxes on on the inside of the sponson's to gaurd against fire and fragments) and a small patch infront and to the sides of the driver, I dont find any proof that the whole machine was thicknd.
My point is this, every book I ever read had the Americans putting railroad sleepers,sandbags,logs,dead bodies etc. on the front to try and provide some protection, this isnt because they where exclusivly afraid of panthers and tigers..., heck I cant find a picture of anything bigger than 37mm bouncing OFF a sherman, but ill keep looking.
I've always thought this tank had a bit to much going for it, mabey the addition of some anti tank guns would put the ronsen liter back in its proper perspective...