Mrev95

With a 12hr rotation period, the centrifugal acceleration at the equator is 3840000*4*pi^2/(86400/2)^2 = 0.081 m/s^2. With a 24hr rotation period, this is 3840000*4*pi^2/(86400)^2 = 0.020 m/s^2. (The acceleration due to gravity is 9.81 m/s^2) This is a 0.012 m/s^2 (= 0.1%) difference. I would consider this negligible, and I do not think that the mass of the planet would need to be increased to compensate for this effect.