Keep in mind that quite a few of the numbers published are from the designers calculations not from flight test data. Analyze the design for performance and see how close you come to the numbers they publish. If you are conservative you should always come up with a lower estimate of the performance than they publish. Since you have the design data you can do a stability analysis of the aircraft. I can guarantee that you what you do will be more comprehensive than the original designer did.
Most homebuilt designers undersize the tail.
The designers of homebuilt aircraft are usually not aero engineers. Since you have the plans you can also do a structural analysis and see what assumptions they made. You can also get practice drafting the parts using a cad system and find out how much work went into drawing up a airplane. When you draw up the plane you should redesign parts to reduce the number of parts and make complex parts more simple. This would make a great Sr. project no matter how many times people do it.