Q: Jason – According to the attached picture do you think I bought a Chimney Pillow that is too big? – GJ
A: GJ, You absolutely bought a Chimney Balloon that was too big. I would say it is at least 6″ too big in 2 dimensions by the look of it. It is hard to tell the dimensions from a picture like this, but I am willing to bet that is a 9″x9″ flue passage that you stuffed a 15×15 Chimney Ballon into. You would be much better served by using a 9×9 Chimney Balloon for this particular spot. But you did do the right thing by purchasing an HEK extender to install your Chimney Balloon so high in the flue. Without the extender, you would have had a terrible time getting the Chimney Balloon that high.
Actually, you may want to consider using a larger Chimney Balloon closer down to where your damper was. I see you had your damper cut off when you had the lock top damper installed. I can tell you have a locktop Lymance chimney top damper by the cable that runs along the side of your flue. The Chimney Balloon will inflate around the cable just fine, but be sure to wrap some tape around the cable where it will come in contact with the Chimney Balloon. Cables like this often have rough frayed edges that will poke into the Chimney Balloon when you inflate it into place.