Applying Centering & Totem Bonuses, The when and how much question Options

[Friggas Ring]

I consider myself pretty familiar with the magic system in Shadowrun, but something about the wording for Centering and Totem Bonuses has me confused.

Let's say I get a 2-Dice bonus to combat spells from my totem. I have learned Centering and have a pretty good centering skill. Confronted by two gangers, I decide to take them both out in one hit. Splitting up my Sorcery dice evenly (assuming I have a skill of 6), I use 3 dice for a Stunbolt at one ganger and 3 dice for a Stunbolt for the other ganger.

In the description of Totem bonuses, it says that I apply the two dice after everything else, so do I the two dice to each spell or do I divide it up amongst the spells I cast that round? While I realize GMs have the final say, it would seem really broken if I could cast one spell per turn per sorcery die, using one die for each spell and then gaining my totem modifier on top of it.

I have pretty much the same question about centering. If centering for successes is a Free action, could you center for each spell you cast at once? Granted, you would still need to succeed with the actual Sorcery die you roll, but if you cast six spells each with one die, some of them are going to succeed.

I'll take opinions and comments, but if anyone could canonically prove that a player could or could not do it, that'd be great.

-fr