Oh.. thanks for the correction Gareee. I was wondering about negative displacement as I typed. I should have wondered a bit further.

In that case, by my calculation smalll's full red in her displacement map would give an inward displacement of one-third of the maximum.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)