I ordered a plus size as XL was not available.  Interestingly, I received an XL, which is the size I needed!?!  I am quickly becoming a fan of Mordenmiss, as their styles are comfortable for warm weather and hide my flaws.

Update:  I noticed that the plaid was slightly sloping on the front of the dress.  I won't wear it for nicer functions as I find this unacceptable.