BTW, the -8 is only certified to 43.1k - while the airplane is fully capable of going higher, the FARs have changed with regard to depressurization. As a result, I doubt you'll ever see another Part 25 airplane certified to above 43.1k
I fly several cert'd to F450 and F510. Several recently were cert'd to F510 and several more in the works. About 30 knots either side of M.84 in the Global at F470.