Jack of some trades, Master of none
succinctly putIt sounds pretty straightforward as I write it here, but there was a heck of a lot more faffing than the description suggests!
I like your bearing solution very much. I wondered before I read the rest of the post - whether there was some special high speed cage option.
Out of interest, why not go down the route of making a brass journal setup and using an oil pump for pressure lube? It seems to be the simplest setup for turbos anyway.