Star apprentice Matthew Chadwick drops to a five-pound allowance tonight after turning over favourite Brett Prebble in Sunday's Jockey Challenge with a treble, and looks the value option to do it again at Happy Valley. Prebble was posted the 2.8 favourite by oddsmakers in opening markets last night and a full book of rides give him more chances to score points than any other rider, with even Douglas Whyte missing two events. The challenge has a fairly open look about it, with Prebble, Whyte and Chadwick all looking strong hopes and one or two other riders could bob up without a surprise, so 2.8 about Prebble winning looks on the skinny side. He has two of the shorter-priced runners in First Baby (race four) and Perfect Style (race eight) but will need to make something of the remainder of his book to make 2.8 look a reasonable price. Second-pick Chadwick looks a far better risk at 5.5 with a number of solid chances headed by Single Malt in race three and Regency Kingdom in the fifth, and all six of his mounts have claims to landing valuable points. Whyte supporters, more used to taking tight odds, will relish the chance of an unusually generous price about the Durban Demon, who was posted at 6.0. Whyte kicks off with a strong chance in Dragon Boy in the Class Five, then another serious contender in Steel Nerves in race three, and he has chances in the last two events as well.