Biggest brakes for 15inch rims??..

You don't want floating discs for a road car, too much hassle, noise and expense. Yeah AP do a strap drive disc. Looked into it, but deemed it unnecessary for my application!

All the strapdrive does is allow the rotor to move side to side a little, which ensures the clamping pressure on the disc is uniform on both sides, rather than 'bending' the disc away from the strongest side like push bike (and badly setup) motor bike discs / calipers do.

OEs already employ a neat solution for this problem - sliding calipers

Without opposing pistons, floating discs are completely pointless.