Stability of different strengths of the same formulation

Dear Sir,

if we have a product of 80 mg Ketoprofen in sachets (Granules for oral solution) for which full stability design has been performed, and now we want to register Ketoprofen 40 mg with the identical formulation and the same packaging material, but half-size that of the 80 mg strength. Which reduced stability design can be acceptable for the 40 mg? Which time-points should it be tested? What about the validation of the manufacturing process? Can it be used that of the 80 mg strength?

Thank you!