I've now done my figures and I've decided to stick by my provisionals.
The times on the day aren't entirely helpful and I've ended up with different going allowances for the sprint races and 10f-12f events. The 'in-betweenie' is Blythe Knight but even the more generous allowance only brings him out on a par with the face value of the collateral form in a race which struck me at the time as being slowly run for the first half.
Normally, I'd be tempted to go with the fastest handicap form and apply the going allowance to the conditions races but Raceform say the pace in Zaham's race "was not that strong" and the fact that the first three all raced prominently would appear to back this up.
On times, Zaham (OR93 / RPR 103) works out 22lbs behind Authorized. I have that figure for Zaham to the ounce on collateral form, so I'm really left with no option but to rate Authorized 125, as above. I do think he's better than the bare form, though.
I also experimented with my 'take the winner out and how would the rest of the race work out' approach.
Had Eagle Mountain won by 2½ lengths and more, I'm sure plenty would have been hailing him a decent Derby winner, but that brings me back to Oath who won by a similar distance, was hailed a good winner and ended up being proven to be well below average. Lucarno (OR93), Salford Mill* (105) and Kid Mambo (104) are all too close up for comfort.
*How on earth was this horse 8/1 second favourite for so long?