This is a mix between a DIY question and an applied physics question, but I figure the folks here are more interested in these details.
My application is attaching a projection screen to a frame with tension to stretch the screen flat. One of the recommended products to do this is bungee balls. In my case, I am considering replacing the bungee balls with extension springs because I can affix them with a twist-tie on one side and it will be easier to attach/detach the screen on the other side. The specifications for extension springs are well detailed (e.g. spring rate measured in lbs/in, but I can't find any equivalent information on bungee balls. How can I find this information (my Google-fu failed)? Or is there a simple test I can do with a bungee ball to measure the spring rate?