Considering Beebe is still learning the center position, and Hoffman played mostly at center in college, and also that Beebe was a top guard in college, I'd move Beebe back to his natural position at guard and put Hoffman at center.
But if you don't do that this year, then I'd leave Beebe at center, I'm not a fan of the "jack of all trades and master of none" player. Continuity on the line is huge, shuffling players around isn't good for continuity.
But if Beebe is left at center and Hoffman replaces Martin, don't think that'd be a bad thing, both appear to have the potential to be really good at either position. Both are young as well.
Nice problem to have...