I agree with JavaCo. There's some indication that 3000K high CRI is the way to go so mixing some 2700K 90CRI with your 3500K would be a good deal.
That was the mantra back in the day, drive Vero's hard because they were good chips but couldn't keep up with CXBs at low currents. They do have a nice thermal package but will benefit from lower currents just like other cobs. If you're wanting to bump your wattage from high 200s to high 300s, consider running 2 or 3 Vero29 C (67v) at 700ma using an HLG-120H-C700, would give you an extra 90-135 watts, very efficiently.