Keep it simple
Call SSS office, I hope they will confirm that you don't need to register for SSS - if you were over 26 yrs when attained PR status.
For me it was straight forward, she asked me about SSS and I provided the letter and explained about being unaware of the process.
>Based on your experience, did they take your request over the >phone? Today being a federal holiday, I cannot contact them.
I got letter in about a week!
>In the event they don't take phone requests, I am sending a >request letter along with supporting documents by UPS today to >get a letter from them saying indeed I am OK.
Unfortunatley the letter will not say you are OK. It is a Government document - it talks about Section, Law, Ammendments,.... etc
INS senior officers will recognize this letter (I had Jr. Officer and she went to check with her boss about letter).
I think if you have letter or not, you should be fine. I completely agree with Joe, it can't hurt to check with SSS office.
Thanks