i don't believe that masteron itself is going to keep you much leaner than if you were to cycle without it. your diet is going to play the majority of that roll. i don't like to look at certain drugs as "cutting" drugs, since they don't really get you cut. more so, i'd call them hardeners. if you're lean and have some muscle, hardeners will give you a more stone like look. this is the main reason that most people use them. but that doesnt mean they aren't still anabolic steroids with the ability to help you add mass. they may not be the most ideal steroids for mass gain, but a DHT based steroid like mast is going to effect the androgen receptor differently than your test or deca will. i could see some benefit in that during a mass gaining phase. so i wouldn't use it with the plan to look leaner while bulking, if thats what you mean, but i still think it could help you reach your overall goal. not to mention, mast ramps my sex drive up by 200%. that could help a brotha out if he were to have sexually related side effects from the deca in this cycle.
also, 20 min of cardio post training, 5 days in the off season is a good plan to have, just to help with hunger and keep your heart in condition. a lot of guys get lazy but i find that if i keep on the ball with a small amount of walking and i keep hitting abbs regularly in the OS, i come out a lot better when its time to diet.