I've chosen to use use a single footprint for both 0.65mm and 0.635mm pitch parts.

0.65mm and 0.635mm differ by only 15 microns. That's not much.

If one were to try to mount a 28 pin 0.65mm pitch package on a 0.635mm pitch footprint or vice versa, the maximum misalignment (measured over the 7 pins from the middle of the package to the end) would be less than 100 microns - about half a leg width. Using wide pads, positioned midway between the 0.65 and 0.635mm pitch (0.6425mm) we can accommodate a part in either package.