Exploiting the fact that kings are exempt from the removal test

>! we can construct a discovered checkmate

with 

>! 21

accessories and

>! 2

witnesses for a regicide score of

>! 15.

>! <br> [![enter image description here][1]][1]
>! <br> unique checkmate is 1. Kd3#


  [1]: https://i.sstatic.net/2p36X.png