The Moschevaya Balka bow find featured, of all things, a mortice joint beneath bone strengthening plates! Others have been one piece designs. The V spliced handle into limb, limb into siyah examples are mainly Turkish bows and believe it or not, the joint is capable of tolerating the stresses applied, some bows being well over 100# draw weight. The mating faces are grooved beforehand and you should remember, these cores are covered later with horn and sinew.
Most examples I've seen of Magyar type reconstructions have had handles glued to the belly or to the back of a steam bent, single section. The only spliced sections have been the siyah to limb. I think your main consideration should be handle to limb junction and achieving a gradual fade with the core becoming thinner nearer mid limb so the working part is away from the handle.
In short, I think you're better off using a one piece core.