Just a tip when Shaptons run out of bite.
Get some slurry worked up on them with a diamond plate, soft steel (mild steel will do) or a scotchbrite pad, make sure the stone is damp and have at it. You should get a lot more bite out them and they'll work (kind of) with the really tough steel alloys.
Because you're pushing the stone waaaay past it's normal operating envelope, expect some random weirdness like clogging, a 'wet' stone that'll need proper drying and a few other things that you'll know when you see it. Not show stoppers, but 'odd'. The balance of wet/dry will be different with a slurried up Shapton, with more of a lean to 'wet'.
This also works on Choseras, as they too can run out of bite when the steel has a large proportion of chromium, vanadium, tungsten, etc. in it. It's not the hardness of the steel, it's the abrasive resistant components that cause the difficulty and as these hard/tough parts 'blunt' the abrasive, you need to keep fresh stuff coming into play, which is why having some loose particles running around will tend to keep the stone cutting where as a 'normal' stone won't refresh itself fast enough to work properly.
The mechanics behind why the Chosera runs out of bite is different to the Shapton, but the cure is similar. Again, you'll be pushing the stone beyond it's happy place, but it'll work and it's not like it something you need to do often, because if you need to sharpen these tough alloys often, you need something more capable of sharpening them.
(It's really odd when you run some steel on a 1K Shapton, and the stone feels like it's greased. Shapton 1K stones don't do that...)
Good luck,
Stu.