I have had the same problem; I can't offer an easy solution though.
Try getting it in sideways instead of straight on (it isn't self-lubricating
). You may need to force it. Just try to get part of the edge over and get the rest to follow.
Once your fingers are bleeding and you're seeing red, take a break, then get a small pair of scissors to delicately make a little cut on the side of the round hole in the LE.
This will not cause you LE to tear in half as long as you don't go past the stitching.
Then try again with the get an 'corner' over the edge and try to get the rest to follow.
It is remarkably painful to do, and wish to never have to do it again. I really don't know how people working in kite factories do.