I've been playing with bungees for the past several years now, and quite frankly, I have found that it makes very little difference in group size no matter what the tension is. It's a bit difficult to describe the amount of tension, but I'm partial to a tight bungee rather than one that is loose. I made several bungees of slightly different length using the hooks that come with them, but replaced the crimp wire with zip ties. The best advise that I could pass on to you is to make up three bungees and give each one a try, shooting 25 or more rounds with each one. I also give the fore end a good coat of wax to ensure that the rifle returns to battery smoothly. As for pit falls, nothing comes to mind. It's really hard to mess things up but it will take a bit of trial and error as far as getting the right lengths.
Hope this helps a bit.
Ken
