Due to the unique properties of the recently discovered sheath laser-ion source the investigation of super-intense, quasi-neutral ion beams interacting with plasma has become of substantial interest. Novel experiments in parameter regimes that bear relevance for future ion based fast ignition concepts can be envisioned. Simulations in three spatial dimensions of protons, charge and current neutralized by co-moving electrons, interacting with a low density plasma are presented. Quasi-neutral beam propagation and normalized proton beam momentum growth are discussed.