Yes Shaun, I guess unders and overs are only as good as the rated price initially. I layed every underlay, based on default neurals as a rating, today but still only broke even. Certainly no gems there!
When you read the extents, man power and money involved that betting syndicates in Hong Kong, employ to produce ratings and still only squeeze a couple of per cent out of utilising every possible combination of betting, it's certainly daunting. And they're in an environment with only two tracks and limited number of horses to rate.
Cheers RP