Wedge - Thanks! Appreciate knowing that my postings and photo's are useful to those who are reading them. It's a little scary though because I certainly would not consider myself an expert at any of this.
A lot of what I'm doing is just applying what I've learned here on TBN from those who are more knowledgeable or have more experience than me.
Eddie - Yes...the 6x6 post are actually a true 6" wide and not 5 1/2". Same with the 6x8's. Thus my wonderment of how I could use a 2x6 stock for the purlin blocking? I angled the nails in an alternating pattern to hopefully better hold things in place, but I think I'll definitely take your advice and add some 3" screws just to be sure.