Sorry have had a good scout around for the book and can't find it! I'm 99% certain it was in the Middleton Press book 'Wenford Bridge to Fowey', if I find it I'll send it on.
As an aside I found the Branch Lines around Bodmin book recently. This says that the maximum load for an 08 on the line was 8 clay hoods (due to gradients around Bodmin). So even in O gauge and minimum space you are almost running full length trains. The book also has a lovely photo of an 08, brake van and a few hoods at Wenfordbridge towards the end of the lines life - I've always thought thats a good starting point for a model! If you want I'll send you a copy - but it'll have to wait till I;m back at work during the week - printer/scanner issues!
Tom