As I was studying potential compnents for our Ann Arbor residential solar array I ran across a new option.
Solectria inverters may be made in the US so that gives them a couple points in my book.
They seem to have a very wide operating voltage range and a wide MPPT range.
And, they are very cost competitive with the SMA Sunnyboy line.
Finally, they do have a string sizing tool on their website here: http://solren.com/stringSizing.html