tap ,with a split like that anything you put on it with bouncing is not going to hold, split will increase and drilling hole is a guess work for the hair line under surface may be pass the hole you drill. without welding it is gone to continue to split and as for alumin rod with torch i have some but that is not going to work .I tried it a few years ago and it buckles your boat and alumin have to almost be at the melting temp for a good stick which going over that point and alumin will cave in. Have it welded and have the confidence without worring will it hold,that is what I had to do. After all you can use other boat or if you wanted to go to kerr you could swing by and get mine, I will be out of commission till almost May if the Lord wills