Every guy made his own choice, you have to do the same. At the end of the day you have to answer to the guy in the mirror.
If you were going to use, there is no reason not to use injectables. With proper research (both here and elsewhere), a good athletic cycle can be put together that will help you put on some size without being (too) detrimental to the rest of your game.
How much size are they expecting you to put on?