I have been wanting to build a MIRV Gryphon but wanted to avoid the cluster ignition, so I came up with an alternative similar to the Estes MIRV where you have a single booster engine but gap staged like the Gryphon version.
I made a manifold of sorts and hope that it will be vented sufficiently to gap stage the four sustainers. I also added a boat tail, shifted the engine back a little and added more booster fin area to help it tumble better. I might have a very small volume where I could stuff a streamer between the sustainer tubes for the booster, but will probably keep it tumble. I may add a dowel to the booster and lugs to the sustainers to keep their noses together, like the Estes MIRV.
I am still undecided if I should stick with the four nose cones on each sustainer, or try to make them piece together to form the shape of a single large cone. Experimenting with both ideas still. This model is basically made from cardstock, except for the balsa fins.