Re non-stock burrs.
I’ve had success with the Mazzer k151H (espresso), SSP Espresso (HU), Gorilla Gear, SSP Cast. All very easy to dial in and all producing stellar espresso (with the exception of the SSP Cast) albeit quite different from each other.
Caedo Opalglide won’t fit and so far I can’t get the Mazzer k151G (filter) to grind fine enough for my Switch recipe (posted on the V60 thread) although I haven’t given up on them as they may be fine for other receipes that require a coarser grind. Looks like the Fiorzenato won’t fit either.
A difference in thickness of 0.2mm (both burrs) is enough of a difference to render a burr set unusable. This is not only true of the Duo of course. And by “won’t fit” I don’t mean I can’t easily get them into the burr carrier, I mean that they either won’t grind fine enough or the flow rate from each grind/pour is unpredictable.)
I’m interested to hear from anyone who has tried non-stock burrs. However given Niche’s stance on voiding the warranty when using non-stock burrs I understand if members are reluctant to share.
(I have one Duo still with the original stock 151F filter burrs - rather good for my taste buds - and I use the other Duo for the risky business of trying a range of other burr sets.)