Steve,
I have forge welded before,all though, not for use on a knife. This will be my first knife. I can not answer the last question because I do not know the answer.
As for material, I have some 4140, and some 1095. The thicknesses on the steel is as follows, 3/8" and 5/16",respectively.
From what you said Thomas, it looks like I will be using a 1" wide billet,which could yield a knife of the size that I want as far as width goes.
With the thickness of the steels that I am thinking of using, if I start with three layers that should be easily forged by hand.
Thank you both for the replies. Keep them coming, I need to know all that I can before I start.