I have read that book and do think it’s a great resource. However, there is also this: The influence of preliminary period in handgonne shooting - Ethnographic Arms & ArmourI disagree ... I don't see any practical need for use of a fuse on handgonnes.
The ignition is still instant, albeit the combustion might take longer in milliseconds. In regards to 'packing' serpentine, or more correctly, mealed powder, packing it too loose resulted might result in a fizzle whereas packing it too tightly and it may not fire at all (not enough O2 on the surface grain to combust). This is why the chambers were dsigned as Richard posted above.
FYI, there is a complete chapter on the development and use of the early black powdahs in this excellent book:
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While it’s original research on a forum, it does make sense given the context of period art and touchhole design. The Veteran Arms website repeats these claims, which does not necessarily give them any more validity, but is why people are trying it.