IMHO a nose ring for a .52 four-stroke engine is not needed. Could it be that the rubber bushings are worn out and need to be replaced? I have used the DuBro soft mounts on engines ranging from .46 OS two-strokes, .72 and 1.00 Saitos and also 1.8 Super Tigre two strokes. None of these engines has exhibited the behaviour you describe.
It is important to put some oil (castor is fine) on the rubber bushings when installing them in order to prolong their life.