I can’t find my single engine Cessna book. But the author mentioned that spin and aerobatic characteristics became poor / dicey with extra weight foreword of the firewall. Hence O-320 STCs prohibiting spins. (Maybe a great STC for Poobs?) However, I have zero O-240 experience. I’ll try to find the quote from the Cessna book today, unless someone can find it first. Busy day.
Here's the quote you're looking for:
http://www.cessna150152.com/forum/ubbthreads.php?ubb=showflat&Number=530231#Post530231