[MT-AU Public] Upgrade from 5.24 to 6.31 possible ???

Hi guys, just wondering if somebody can confirm if I can upgrade from 5.24 straight to 6.31 on an RB1100 ?? I thought you needed to go to a later version of 5.x first before upgrading ? When I try to do the upgrade from within the router itself it says that the latest version is 6.27 and then complains that it can't find one of the npk files and aborts the download. Thanks Paul