I have had some lift shackles made from a cousin. They are 10mm thick stainless steel. Will they be strong enough. People are saying they arnt and they'll crack. I'm not 100% sure of the grade but for the meantime will assume they are 304 Stainless. That gives it a yeild strength of approx 30,000 PSI before they start to permanantely deform.
This should be strong enough right. They 200mm long 40km wide and 10mm thick.ill try upload a pic.