Excessive down trim in 8' Beaver
quote: "It's not an aerobatic aeroplane"
Yep and it's not a high speed aeroplane.
Your doing nothing more than driving to fast, come back on the throttle...a lot!
If you want to burn up the sky, don't use a beaver or mix some down elevator with throttle... even then it'll get stroppy with speed.
Kicks from this aeroplane? Sharp/steep side slipped handings... you can't find a better aeroplane to perfect your technique.
Enjoy.