I've never used bungies so I can't comment on them specifically. I did do research on them because it seemed like such a great idea and would be fun to make. The main problem with them that I've read about is the fact that your tent stake will be a projectile if it loosens and comes out.
While I'm not as experienced as some on here, I have been on quite a few trips. I've never had a problem with my tarp loosening during the night or rain. I setup my tarp when I get to camp and then do a quick tightening as I go to bed. The tarp has time to stretch out before bedtime.
My rig uses the dyneema guylines that have a polyester sheath. They don't stretch like nylon guylines. I have a loop on the stake end. The other end goes through the tarp ring and ends back on itself with a tautline hitch. The lines are always left on the tarp ready to go.
This setup accomplishes a few things. The line slides through the tarp side instead of digging through the dirt if your stake is buried on the stake side. Having the adjustment on the tarp side also allows you to reach out under the tarp if you do have to adjust instead of going out in the rain. You can't loose a tautline hitch and it can't break like a commercial adjuster.
Hope this helps. Just my opinion.
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