Mike, once you get this welded, leave your boat tied down loosely on the trailer. I think this cracking is caused by boats being tied to tight and when the trailer flexes while driving, the boat flexes too. Aluminum does not have the flexing quality steel does, and therefore fatigues and cracks. My old Willie had some welded cracks and after I was told to loosen up the tie down in the rear, it never cracked again. Also, when stored, loosen the tie down completely.