Donnelly says for the 7x66 Vom Hofe SE to use .404 brass (10.75x72mm).
.545" base. Turn rim from .537" to .510(rebated)& cut a new extractor groove - trim from 2.86" to the length of 2.58".
The writeup also says you will need a case form set of 3 dies to make the 7x66 Vom HOfe SE.