It does look cool and reminds me of the years long ago when I was a poor kid.
However, I do have concerns about those band loops. If they catch the projectile, they may probably send it back to you with fearful force. I have passed my youth, so only straight and clean bands or tubes. No loops, pockets, or the like.
Got to shoot it today.it is pretty serious for some rubber bands. First time I shot the snap jaw and had a few fork strikes which I Hadn't had with any of my other slings.Couldn't dial it in with 3/8" steel. It really liked the marbles. It isn't as wide as some of my other slings so it always felt uncomfortable. May need to be 1/2" wider. That is the great thing about making your own you can get the right fit. Might back off on the power. It shattered the plastic catch tub.