How do you apply Modern per stirpes?
The estate is divided into shares at the first generation leaving survivors. It is "per capita" at the first level that has survivors, and "with representation" after that.
Under this approach, one looks first to see whether any children survived the decedent. If so, the distribution is identical to that under English per stirpes. If not (and all of the decedents children are dead), the estate is divided equally (per capita) at the first generation in which there are living takers, which is usually the generation of the decedent's grandchildren.
Any deceased descendant is represented by her descendants using an English per stirpes distribution. This system treats equally each line beginning at the closest living generation.