The cat cut is to achieve a taut tarp, not maintain it (as well as saving a little weight with minimal loss of coverage), a silnylon tarp stretches a little, and more when wet so it is the bungee that maintains a taut tarp and saves the need to adjust guy tension. If you have a poly tarp or cuben then the bungee is less necessary.
I think most use 6-8 feet for guys, I'm still playing with mine to find the best set up for me.
I'm sure someone will post a link to how to do shock cord tensioners (I'm on my phone so it's difficult) I know headchangeforyou done a tutorial.
Hope this helps.