Red oak is good bow wood. It needs to be wide. 1-3/4 would be the minimum I would use at the fades.
Also you guys are missing the biggest advantage ( in fact one of the defining factors) of pyramid bows: They do not taper in thickness. If your limbs taper in thickness, you can probably end up with a good or great bow, but it's a different design, not a pyramid. And, if the sides have a straight taper and the belly tapers, you won't have circular tiller--another defining point of a pyramid design.
I have never liked the term "pyramid" for the design that is called that. The limbs are much closer to an obelisk than a pyramid. I think it would be more useful to call it a straight side taper bow (STB?)