I have a DIY top quilt made from IX and it doesn't keep me wam and makes me sweat. I believe IX works for underquilts because gravity keeps the spaces open between the layers. In top quilt mode, gravity is collapsing those spaces and it doesn't seem to work.
I would highly recommend that your top quilt be made from Climashield or Primaloft. Synthetics are a little heavier and take up more volume than down, but they are inexpensive and very easy to sew.
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