You may not be satisfied with only 300mg per week of Primobolan, and I definitely cannot see you adding much 'mass' using this dosage, or the fact that you will be needing to stay lean for a contest.
You can't bulk and cut at the same time. You have to decide what you are doing.
My suggestion is that you keep your calories high during your 'off time' Also don't go fully off, as you will just be begining to recover from the deca use at the 6 or 7 week mark before you go back on cycle. It is simply a waste of time, and will really weigh heavily on your self-esteem regarding doing the fitness show, if you are shutdown, and losing muscle, when you should be getting ready for the show.
I advise that you use 100mg of test enanthate or equivalant per week during this 'off period'. Continue with decent calories to maintain your muscle, as much as possible, and then add in the primo at 300mg per week, and increase your test to 300mg per week as well. This will be optimal for keeping your size while you cut. At this point you can alternate the clen cycle and the eca stack. Don't forget though that diet and cardo are more important, and will burn the brunt of the fat you need to lose.
After you are done your contest and primo cycle, you can taper off on the testosterone by itself for about 6 or 7 weeks.
something like this:
You can use clomid or nolva concurently or after if you like, but I personally choose not to as the whole idea of a taper is to return you body to normal homeostasis.