No need metal. Just hang the targets slightly back from the legs. The splash will miss the legs.
You're looking at the back of the legs. The hardware was attached to the back of the legs, so the targets were basically flush with the rear of the frame. Except for the top target hanging from the top cross bar.
Based on the level of damage, I'd have to hang the targets at least 2-3 inches behind the frame, and I'd need something like a metal bracket to suspend them.
Whatever the targets are suspended from is going to get hit, right?
If anything, I'd think having the targets in front of the frame would be better, since the splash would deflect at a forward angle?
I have a couple of old bed frames made of steel I was going to try and use. Haven't taken the time to really look at how to do that, but seems like a good recycling project!