Hi Frank,
"I think in the spirit of the book it is mandatory to do it cubeless, without Jacoby."
Without Jacoby I understand, but why cubeless? While Magriel is a bit short on cubing, but still he has some problems on doubling and in some positions a cube is displayed.
"Then the problem remains what to do with positions where the cube should be given before rolling.... "
Well, that's easy. Where no cube is displayed but it's very obvious that one player should have cubed before rolling, I just assume, the his opponent already owns the cube. That's also how Bagai did it for many positions.
Hardy 