This is one impressing physique there - allow me to congratulate you on such an achievement. It must have been extremely hard to achieve this sort of results naturally, and with a little additionall mass you can easily be successful on the men's physique stage.
Rubber should not make a difference compared to iron as long as the weights used are the same. However, I doubt you can get as much weigth with rubber as with iron. Therefore, for further progression it would be a good idea to use iron.
P.S. I have done the air alert back in the days, when I was a kid and was playing Bball in college - a hella of a programm!