For what it's worth, from all the suggestions and after watching the video I decided on the featherweight fusible interfacing made by Pellon. I've cut strips of it just a tad narrower than the 1/4" seams I'm using for piecing, and I'm applying the stuff to the seam allowances as I go. It's working beautifully even after I did a trial block and put it through the washer and dryer on my hottest settings. It isn't coming off even after picking at it with my fingernail pretty aggressively. Certainly no unraveling is taking place. Wouldn't work for a fabric that won't withstand a steam iron set on the normal cotton setting for 10 seconds, but the fabrics I'm using are all undergoing that just fine - I'm actually using a damp pressing cloth rather than the steam setting.