I was not aware of the "compromise." I did a little checking after reading your posts. It appears a Chinook can carry 13.5 tons on it's main hook, and included in the text is its ability to carry large (155mm) artillery pieces -
http://www.army-technology.com/projects/chinook/
I also saw this picture of an old army helo carrying what appears to be a decent sized piese of SPA.
http://www.britannica.com/EBchecked/...r-lifting-tank
But, as I have now been informed, I didn't see any tanks being lifted (although I know the Sheridan was designed specifically for this purpose)
Thanks for setting me straight!