Brake Caliper Carrier / Disc Sizes

Evening all, couple of questions on the above

The rear carriers on the focus come with a couple of different numbers printed on them, 15 or 16

I don't suppose anyone knows which disc sizes fit what.

I have a feeling that 265mm for the 15 and 280 for the 16 but thought id ask about to see if anyone knows for sure.

Finally, whats the thoughts on running 280s on the back instead of 265s, im aware that it will pull some of the bias backwards but ive been reading in several different places that the brake bias is normally set about 5 to 10% further forward then optimal anyway to aid stability for every day job blogs and the size of the rotor is much less important than the the pad, which as it turns out is exactly the same pad on both sizes of disc.

(having issues finding spare 15 carriers, have a perfect set of 16s though...)

after some crude maths, I think the torque difference between the two sizes of disc is approx a 5% increase on the 280s, the difference between the drums and 265s is actually nothing or as near as, other properties give the appearance of better results, plus it looks better :)

Done some more maths on this, mechanically the car is set to have a bias of approx. 70/30 with 265s on the back, replacing them with 280s changes that to around 66/34.