Paul is the guy to answer the question, but I can tell you about my stabs. Here are pictures of my last two dogs. The white one's stab is per the original plans. The yellow one's stab has half the tip chord of the original. Paul built a couple planes with the reduced tip chord, including the one with which he won every contest it entered, including the world championships. At the time I built the stab on the yellow dog, Paul favored the smaller chord, so that's what I used. He has since reverted to the original chord. I can't fly the yellow plane very accurately. The flaps are the chief suspect, but if new flaps don't help, I might try changing the stab.