Tony Paletta wrote on Tue, Sep 30, 2003 12:50 PM UTC:
(RN,BN) vs (rb,kn) is a valid alternative and would allow full promotion;
in commenting, I opted for the (rbn,k) to retain some of the imbalance of
the original CV.
With either rbn or kn, however, the use of true 'double royalty' and
limited non-royal power might tend to make the variant play a bit slow.