I'd file (or emery paper) the backing plate rather than the friction surface (as I had to do with my Superstar kevlar pads). I seem to remember that once I'd got the paint off they were okay.

It shouldn't be necessary to file the pads. Are you sure you've pushed those pistons right back? Try opening the bleed screw to allow a small amount of fluid to escape before pushing them back. Remember that when you brake, the pistons don't actually move through the seals, the pistons are an extremely tight fit in the seals and the seals just distort under hydraulic pressure then rebound. The pistons do creep through the seals but that's over hundreds of applications as the pads slowly wear. If you haven't pushed the pistons right back, the seals will be bringing them back out and leaving you insufficient room for the new pads.

I measured the ones I had and compared them with EBC branded Hope equivalents. I can't remember the figures but the Superstars were significantly thicker and I think it was all in the backing plate as well.

Let a bit of fluid out. Seems fine now. Cheers all.

This is why I only fit the manufacturer`s pads..push the pistons back, and put the pads in. Those that are old enough, will remember this was one of the selling points, when we evolved from braking with wires and blocks of rubber..
No need for bleeding or filing, its meant to be an easy job, why make it difficult?

You're lucky it was just a bit thick, one of the last sets of Uberbike pads I had one side stamped out wonky and wouldn't even fit in the calliper! I've gone back to Shimano as well.

This is why I only fit the manufacturer`s pads..push the pistons back, and put the pads in.

Not if they've been overfilled.