Back to the drawing board... stock low dollar 360

The FBO plate limits the wrong end for best power, otherwise its a clever and handy way to reduce the total.
If using the plate, some of the secondary curve can be regained by turning the secondary (long loop heavy diameter) spring perch for earliest contact.
Whether the primary spring perch needs adjusting will depend on thespring and rpm it idles at. With a lighter spring, it will probably need more initial tension.
That might be why it was was bouncing at 10*