sorry for not being here in a while, but yeah basically I found out shackles are real easy to fabricate. And unless you get them from a store, shipping would be horrendous for these shackles as they weigh quite a bit. I built mine in the basemente with a homemade jig for my drill and that was it, start with a small drill bit and go up to 9/16" in 2 or 3 steps, makes it a lot easier, don't forget to squirt some lubricant on there or else the bits will go dull in no time.
As for the bracing, I thought of it for a while, but that's when I decided to go with the 1/2 flat bar, its a lot thicker than one is used to seeing. From other applications i'Ve seen 1/2" flatbar being used (heavy machinery, forestry equipment and stuff) they will not bend, plus they offer nice flex. Also another way to see it is;
Note: and
only for 1/2" or thicker flat bar, is that if the strain put on the shackle (from off roading) is strong enough to bend it because it doesn't have cross bracing in the center, thank your lucky stars you didn't have bracing in there, cuz if that shackle doesn't give a little, its going to be your frame that'll twist into a pretzle

: but other than that, these will never bend, and when they do, such as when rear ended or something, my frame will stay nice and straight... I'm open to opinions...
Have a nice day, and by the way they really add a beefy look to the rear end