There's nothing 'wrong' with the designs but there's not a design out there that can't be improved. It's just the nature of engineering. You learn from the first ones off the line (or out of the garages/hangars in this case) and then make a great design even better.There is nothing the RV-7 structure need to be a safe and proven aircraft. There's a reason there are more RVs flying than any other homebuilt design.