Weight your Loose Ends
Our favorite weights are electrical insulators. They aren't very expensive and they do create weight. For loose ends, we wrap the ends around the round "donut". Then, we use shower curtain "gourd" shaped wires to hang them. If we need more weight, we just add another insulator and/or a fishing weight.
Using a loop of scrap yarn to pull the end tighter works very well because as we advance the warp, the weight "automatically" moves down with the warp.