A design idea has presented itself where I want the sprang to run in the weft direction instead of the warp direction. (Why don't I just work as usual and turn the piece 90 degrees? Because in the same piece I want the sprang running in both these directions.) Here is a sample I put on the loom to see if this is possible.
One thing I didn't think of before I started in on the sprang work was that since in the wefts are not under tension, the middle section started to buckle and pull in as soon as I'd done a couple rows. So the tension on the yarns being worked had to be kept fairly loose.
To get this required ease, the wefts that have been worked in sprang were left longer than the width of the fabric. They are hanging down off the selvedges at each side of the fabric, not visible in the photo. These were left hanging out so that they could be pulled through the weaving on either side of the sprang, to give the ease needed as the work was progressing. This was not easy to do as the yarns had to be pulled through 3 inches of weaving on the sides. In fact, it had to be done one thread at a time, so it was difficult to control how much each was pulled, and hence the resulting sprang work is not as neat-looking as when worked with the warp. But I think this will work.