So, say I have a buckler in each hand, one a +1 blinding, the other a +2.
Now, you can only have 1 shield slot at a time, so which shield do I benefit from? Do I choose from round to round, moment to moment?
Now if it's still relevant, imagine I attack with the active buckler hand. Does the inactive buckler automatically become my active buckler at the moment of my attack?
"You can also use your shield arm to wield a weapon (whether you are using an off-hand weapon or using your off hand to help wield a two-handed weapon), but you take a –1 penalty on attack rolls while doing so."
So a weapon in either hand would take a -1 penalty because of the shield and you would only be able to use one of the shields anyway. Doesn't sound worth it.