How do I specify custom Novus Search options for a given Cobalt Search module search type?

For a given search type in Cobalt Search (e.g. ResultTypes.KNOWHOW defined in WLNSearch/config/wln/spring-results-types.xml), how do you specify custom settings for the Novus Search object (e.g. Search.setDocumentPortion())?

I see in spring-results-options.xml there is way to specify a Map of SearchOptionType to value for given search types, but the options supported by SearchOptionType are limited and it's not immediately obvious how that eventually maps to which value is actually set on the Novus Search object.