Anyone else check out the chess variant by Seirawan and Harper?

This is the Wikipedia entry:
http://en.wikipedia.org/wiki/Seirawan_chess

The configuration starts the same as in regular chess.  Whenever a
piece in the back row vacates it spot and leave it open, the player
has the option of entering a Capablanca piece (Knight-Rook or Knight-
Bishop) onto the board into the space vacated.  The Knight-Rook
(Elephant) and Knight-Bishop (Hawk) are two pieces that remain off the
board and can only enter when this happens.  It is a double move like
castling, and works like en-passant in that you get once chance with
the original piece moving off to do that.

I was curious if anyone here had seen it, and your thoughts.

It had been going by Seirawan Chess, while Mr. Seirawan would like to
credit Mr. Harper for the design also, as he worked on it.  I might
propose Sharper Chess as a name that might credit both them (S from
Seirawan combined with harper for Harper).

I see a variant off this where players before starting, can decide
whether to have a queen, elephant or hawk in the queen space to start.

Any comments?
- Rich