Uhhhh, Deca only cycles are not fun from what i understand. Ever heard of deca dick? It will shut you down HARD.
Don't do a deca only cycle, not smart, and the fact that you are asking this question shows your lack of research.
Do more research, id you had just typed "deca only cycle" in google you would see very quickly why it is a bad idea.
You are supposed to run test with deca to avoid the awful shutdown sides, but you need to do way more research man.