Need a rules clarification. I have an upcoming Apoc game and I plan to take a Warhound Titan with two Double-Barreled Turbo-laser Destructors for its arms. One of my opponents is complaining that that shouldn't be legal, that you can't take two of the same weapon type.

The book says "two of the following arm weapons" but does not say anything about disallowing two of the same weapon. Thoughts?