I have contacted Prof van Valkenberg directly: she has kindly supplied a .pdf of her 1990 paper, and is happy for it to be passed on.  If any have difficulty getting this, please email me or her directly.  

Like all the other chapters in Damuth and McFadden (eds.) 1990, van Valkenberg shows the relationship between size and weight is allometric (exponential); simply multiplying one dimension by some constant will not work well. 

Greg Campbell

The Naive Chemist