G'day Gregg. After a bit more research it appears we can go up to 330mm with 17" wheels. There are a number of 4 and 6 pot kits on eBay to suit VZ - search for Ksport or D2. These are probably made in China and not ADR compliant, which puts me off.
Next one I came across was a VF-spec upgrade kit with 322mm rotors, ebay item 181218009835, pictured below. Only twin piston but looks like a different design to the earlier calipers and the larger diam rotor will help.
A couple of places are selling an Alcon kit with 335x28 two piece rotors, 4 piston calipers, adapters, etc.
D2 Coilovers - Fifteen52 Wheels - All at Tuner Warehouse - Alcon Brake Kit Sale - 4 Spot Monoblock 335mm Kits just $2500
Brakes Direct - JANUARY SALE: Alcon 4 Piston Caliper Upgrade Kits! / News
This video taught me a few things and features the Alcon rotor:
Plenty of suitable AP / PBR / PWR kits here:
Holden - Performance Spares
Also found a "PK1" kit on eBay using VE calipers and another "BAER Pro" 6 piston kit with added bling, below. Enough options?
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