I haven?t spun mine extensively, but I have found that spins in my RV-6 (O-320, wood prop, sits pretty far aft in the CG envelope) have been predictable. However, as Mel indicates they change in character after 1.5 - 2.0 turns. For a 1 to 1.5 turn spin the airplane recovers very promptly as soon as you remove the pro-spin control inputs. Beyond that it takes more time, but recovers well with the recommended control inputs. I?ve not spun mine more than three turns. That occured as I was working towards a 2.5 turn spin, and it did not recover until about three. Six must get pretty sporty?
YMMV
Doug