Just bought a 2015 525 Sporter One with the re-coil pad fitted from new and I think from doing my homework that if it came with the pad from factory then that's the only time it'll be a straight fit, otherwise it's a grind off job. Part of the reason I was so happy to find a 2015 model as once it's on there you can add the spacers between the stock and the pad to extend, which I need being a big lad.
If I remember correctly, think they started fitting them around 2014.