I'll take a stab at answering this, as it was also one of my questions when I started forging years ago. I had trouble getting a response as well for whatever reason.
I have done this a few times for certain blade styles where the ricasso is the widest part of the blade. Japanese style blades come to mind. I usually forge the preform with a much more aggressive taper in width than I would otherwise. Then when you forge the bevels, you forge the bevels lightly near the plunge and more heavily as you go towards the tip.
You can also forge a small step in your preform at the plunge and then forge the bevels as normal, which uses less material and requires less stock removal afterwards. It's a bit trickier to do this, if you are shooting for a certain size blade, until you have enough experience to know how much steel you need to start with to end up at the final dimensions.
Hope this helps,
Darcy