I wouldn't use them if they're oil-based. Oil paints dry to a hard finish with no room for flexibility. They also tend to dry really, really slowly. If I've done my research right, I think the addition of the acrylic is to help it dry quicker. This is a confusing subject because people, and myself, generally associate "acrylic" with water-based latex paints. But if it is an oil/solvent based paint, I would NOT use it on a medium that flexes.
What kind of paints are they- Tamiya?