crupper help!

["guest@endurance.net" <guest@endurance.net>]

Tiffany D`Virgilio tiffshorse@mindspring.com
I can't seem to post from my email address, so I am here as a guest:(
I need to use a crupper for my mare, but she is not to hip to that idea. Everytime I get it semi-on, she just about sits down and dies. She is even funnier when I try to remove it and she clamps down so tight I can't get it off. Help! Any tips to ease her into the change would be very much appreciated. She will let me work on her tail to braid, brush and wash it, but crupper-no way! She also will sit down if the hose gets under there during her bath. She was bred four times and lost three foals before I got her, so I really had to be gentle around her tail and vuvla area at first. She was very sensitive! 
Thanks, Tiffany