The only problem was the writers eventually decided the viewers wouldn't care who was who.
In S2 Tony says "I'm bumping you and Sil up to caporegime and Consigliere respectively". And by pecking order, I think he was just referring to the chain of command. Like back then, Paulie and Silvio would have authority over the captains. And it's definitely true for a while, soon after, they get to order Richie (a captain) to build a ramp.
That's just it. I don't remember Tony ever saying that. He had that meet up with Paulie to tell him he was bringing Furio over. And then Tony said something like "It's me, then you and Sil together. Pussy answers to you guys. Furio too." Maybe people read more into that than they should and just assume Paulie was the underboss.
Despite what various fan sites or wiki sites say, I don't think Paulie is ever identified as the underboss in the show itself. But he is often identified, either directly or indirectly, as a captain in various episodes through several seasons. Also, Silvio was identified as consigliere once or twice.
