Hi Tom,
There are a couple things you can try to help this 
This won't cost a dime......................
The bolt rope was bad for shrinking on the factory sail.
If you can hang it between two solid points (a couple trees, or something like that)...........
Chain the tack to one tree (chain around tree, post or whatever, with a quick through the tack and ends of the chain)
Attach a come along to the other tree, or other anchor point, and in turn attach the come along to the head of the sail. Stretch the bolt rope, using the come along. Leave it stretched like this for a few days. You can wrap the rest of the sail up onto the tensioned bolt rope and tie it up, to keep it from flogging, during this time. Don't over do the tension and tear the sail.
This will cost, just a little.............
Carefully examine the ends of the bolt rope at each end. You will find the stitches that hold it in place. Carefully remove these stitches to free the bolt rope. Now, you should be able to pull the bolt rope out of the sail.
Buy yourself a new,
pre-stretched bolt rope from Sailrite, of the proper diameter and install it in the sail luff. It's not too dificult. you will need something stiff, that is a couple feet long to use as a fid, to get the bolt rope fed through the luff. (I have used a piece of an old fishing pole for this, after removing the line guides. A fiberglass tent pole section also comes to mind). Attach this to the end of the rope with several wraps of good, sticky tape.
Once the rope is completely through, re-stitch the head end, by hand. You need a foot or two of rope to remain hanging out at the tack end at this point.
Now, starting at the head, where you just stitched the rope in, pull and milk the sail cloth along the length of the rope, to pull out all the wrinkles you can. Mark the rope where it exits the sail cloth with a magic marker. Now you can bundle the whole mess up and go sit down somewhere with it and re-stitch the other end (the tack end).
Another way is to remove the old bolt rope and stretch the crap out of it for a few days, by itself and then re-install it.
This should be a major improvement. I've done both of these methods on a couple of old mainsls and it helps quite a bit. I think replacing the bolt rope works best.
You will need the bolt rope itself, some thread (T-92 or similar, I would say, but call Sailrite and ask, they are happy to help), a good, large, hand sewing needle and possibly a sewing palm (I've gotten by with pliers in the absence of a palm).
Try the free method first, then decide if you want to go on.
This, by the look of the pictures you posted, should improve things, quite a bit.
Best Breezes,
Steve K.
) college and all. 
Donno, but it doesn't look like any Cunningham, I've ever seen (although I don't know everything by any means). A Cunningham is usually just a a grommet placed several inches above the tack, on a sail of this size.