My friend Cindi made this pretty quilt - not exactly scalloped, but it's another option. She used EQ to figure out the size and layout of the border. Do you have EQ? That would be a great place to test out different options!
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http://www.seamstobeyouandme.com/wor.../2011/05/2509/ (the finished quilt)
http://www.seamstobeyouandme.com/wor.../09/i-love-eq/ (details about the border)