Agree with Wells. 0.3mm is the thickness of a coat of paint.
That said, they look as ugly as sin.
Really? I'm kind of surprised. For a difference of 0.3mm you wouldn't run them?
If your bolts line up, the offset is the same, the disc/pad contact area is the same then who cares what the hub size is so long as it fits?
I guess .3 might as well be 30mm.
Then you are only only relying on the bolt holes to make the disc run true /concentric.and if there is a fair bit of clearance in the bolt holes the the disc will have the potential to oscillate.
And the run out will be far greater on the out side diameter,giving a pulsing affect.
You are also relying on the bolts to stop any radial movement. rather than the locating hub on the wheel.
The possible worst case scenario
the disc could have the potential to flog it self out on the bolts.
or the bolts to shear under load,thus no brakes, but hey you still have a back brake.
But hey you two are the Engineers you can sign of on it
And +1 on the ugly bit
And to quote Betty, Believe post content at your own risk.