You may want to try using 2 heddles at the same time (2 heddles of the same Heddle Dent size). This will allow you to approximate some weave structures of a 4-harness loom. . . or at 1.5 [or 2] the number of warp threads. The threading is a bit more involved and the process is not as easy as a true 4-harness loom and you can't do 'all' 4 harness patterns, but for the occasional need, this is a nice option. If you are interested in doing this, order an extra set of heddle blocks and a second heddle.