HI,
If your worried about the pistons coming out, which it appears you are, you will need to take up the extra space.
Get some 2mm steel shims waterjet or plama cut in same profile as the pad, if they are indeed the pads i thing they are, they are held in the 4 piston caliper with 2 pins so you don't need to worry about the pads or shims falling out.
I hope this helps.
Cheers, Peter
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