well this is my opinion. 20mg of dbol for 4 weeks you will make gaines but i don't really think your will get "juice" notacible gaines. Meaning at 20mg it's not like you will look like your taken something big. DBol is good jump start unless you want to not feel any power or gains the first 4 weeks while on the injections. I think 20 of dbol will be fine to give you the power you need, and some weight to go with it. Not incredably huge. The deca is a good though but i dont' understand why you would start the sys weeks 5-10? I mean it takes 4-5 weeks to kick in. My thoughts is do this...

weeks 1-4 20mg DBOL ED
weeks 1-10 400mg of Deca
weeks 1-8 500mg a week devided into two parts(Monday and Thursday)

The reason why i made sus to 8 weeks is because sus most people should run it AT LEAST 8 weeks to get great effects from it. And like you said you don't want to get noticably big, so I think this is a great cycle... You don't have to take my advise, but that is what I would do if I was in your possition. GOod luck man.