I also just went with the Harken Carbofoil. Hall Spars made a new headstay for it too. It's done, but I haven't picked it up yet. I spoke with Cory Butlin (Blitz) at Hall and he recommended the Harken 7001 Carbo foil that accepts the #6 luff tape - same size as I had on the old Tuff Luff.

If the tape is too small for the groove, it may tend to pull out under load. What size luff tape do you have?