I did make a spiral quilt, but it's something I designed myself. I pieced it using the Ruth McDowell freezer paper method, and I still haven't quilted it. I've got a pattern lined up but it's fallen behind in the quilt queue, plus I'm dreading quilting through all those seam allowances. The quilt top is 22" x 25". It was definitely challenging piecing, but then I was doing absolutely tiny curved piecing, with the smallest curved pieces being about 1/4" x 1/2".
Shell quilt top by
Elettaria, on Flickr
I gradually built up my skills in piecing using this particular method, starting off with a basic quilt I designed myself and then working through the exercises in McDowell's book. Is there something similar you can do, if you're not sure whether you have the skills yet or not?