Yep, you're crazy.
I've shot the duplex PR load before and it performed pretty well out of my Knight. I'm not sure if you can duplicate it like you're thinking about though. It might be worth a try.
Take a reading on them projectiles.. all you might need are some of the blue 10mm MMP sabots, and just change out sabots.
As for your questions.. I do not know if you can duplex a sabot like that.
[align=center]AND[/align][align=center]Yes you are crazy...
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The blue 50/40 sabots from MMP popped into my head as well.