Heh...hard doing this over a forum. Easy to talk about the same thing in two different ways.
Larger as in... physically slightly taller / more chips on it. He seems to have two variations of SIMM.
Has he swapped them? I don't see a post where he says he's tested with Bank A only, he just posted a diagnostic again that shows an error with Bank '2' which I assume is what Snooper shows when it means Bank B.
But yes, other things can cause bus errors.