Thank you Steve for bringing that to my attention and I have corrected my above post accordingly. I was thinking in terms of function and not regulatory which got me thinking and after a reveiw of the US AMA saftey code in this case there is no restriction on a simple nutted crankshaft but there is a listed recomendation and a quote from the FAI sporting code that list only this statement "Avoid using a pointed spinner".
I did find in the AMA competition regulations for example the venue of my interest pylon, a specific rule that states "the front end of the engine shall be covered with a rounded spinner or safety nut". There may be similar such restrictions also for various other specific competition venues but there is none in the general safety code and it is fairly common here to sport fly here with a nutted shaft. Yes I am aware that you and the other gentleman are from the UK and thanks agine for the correction.


John