I would go with the 2 riser system also. if you take the 2nd car out of the same riser as the 1st mod, you still have 2 coherent cars and one chase car.through the rest of the mod.That said depending on the year the Miprom was installed they had a parameter on the later installs called, Hall Call Latch. The hall call output stayed high as long as the input was high, then I think but am not positive that the input stayed high through a relay contact that was used as an interface on a mod.Something to look into.