Apron Rod Issues
I am enclosing a photo (shown below) to help you visualize my issue. The string that ties the back apron rod to the warp beam on my loom has slowly been stretching. I'd like to find a different system, but am not sure what to do.
I've answered this question before for a different loom, but the solution will work for any loom. If you drill holes in both the warp beam and the cloth beam (about 6" to 8" apart), you can insert a length of Texsolv (link-loop) cord through the hole and then back through one of its own loops. All of the cords can easily be cut exactly the same length, and Texsolv cord will never stretch. The apron rod can be inserted in a loop made at the other end of each cord (easy to make by pulling the cord through the last loop at the end of it).
I would also recommend replacing the metal rod with a wooden one. The rod needs to be strong enough to support warp tension without bending, but you'll find not having to contend with the weight of a metal rod will make all of the tying-on steps easier to make.