I had this very setup on strong electrical running .5 nominal to one 12 ZV4 sub. Box was built for two subs ~ 4.5 cubes. Mounted one driver before cutting a hole and mounting the other one, and took all the power that 3500 had @ .5 no sweat. Had to be well into clipping to start smelling coil. Ran it like that for a month before the other sub was installed, now I need more power. I'm shooting for an SAZ-5000 or a NS-1. I'm thinking NS-1 would be more appropriate.
IMO, a 3500 is perfect for one ZV4
I'd run 3 Cubes, minimum of 40 sq inches of port. Tune to 30.