The Super & Strike parts (AKA FAST Packs), were only designed to be used on the VF-1 for use in space, where lift is not an issue. They were not designed for use in an atmosphere.
Anyway, as long as there is sufficient thrust, I'd imagine that drag would be more of a problem than lift as the VF-1's FAST packs were not exactly aerodynamic.
Later VFs, such as the VF-11C, VF-19F/S and VF-17D/S had more aerodynamic FAST packs which could be used in an atmosphere (see M7 ep # 44 Operation Stargazer).
Graham