Hi Max,
if the original blade carriers were hardened in anyway they would not chew the blade bolt holes out the way they do, seems like ms plate to me and the only way I could see it putting any stress on the bearings is if it was out of balance but they are big heavy bearings so I don't see any issues but as you say it is a fair bit of work. Rover ones are too light and too small in diameter and I would still have to make up a spacer to fit over the end of the spindle shaft and bolt up to the 4 bolt holes
