This is the best example I've come across for why the cardboard cutout method should *NEVER* be used to estimate CP. It very reliably estimates a CP forward of the actual CP; in a rocket with pretty marginal power anyway putting enough weight in the nose to put CG ahead of that estimate means you're too slow off the rod for the fins to matter.
The cardboard cutout method should be decapitated, its mouth stuffed with garlic, a stake driven through its heart, burned to ash, and then buried at midnight at a crossroads.