Just run the test for your first cycle, it should do you just fine with that... in my opinion i think you get the most out of deca when you run it for at least 12-14 wks... at least thats how its been in my experience...
i would wait til your next cycle to throw the deca in there, this way you get to know how your body responds to test stand alone. Since this is your first cycle see how your body reacts to the test by it self first, if you throw in two compounds in your very first cycle you wont know how each one itself can effect you...
Stick to you test bro and you'll be fine, no need to stretch it your first time using...
Good luck!