There is no P60 trials class here in the UK, and if you have any sort of P65 which is even vaguely authentic, you are at a distinct disadvantage when riding events laid out for modern Brit twin-shocks, which is in effect all of higher level UK competition.
The OIF Ariel ridden by Miller was never a production machine, which seems to suggest any other one off special with documented history going back to before Christmas 1964, should also be designated as a P65 machine, if a vague modern day copy was to be created?
As to modern day Ariel OIF chassis kits, they differ quite a bit from those around in the 60s, with much shorter wheelbase, steeper steering angles, modified suspension geometry, as well as weighing less.
Here in the UK several Ariel riders are also using magnesium top ends, wheel hubs, and gear box casings. However they still weigh considerably more than the very special Cub, Villiers and Bantam based bikes being built now, and are not ridden by anyone competing seriously in higher level events.
That seems a shame to me, but I guess when there are in effect no rules, in a sport like trials the heavier more authentic bikes are never going to work as well as the ground up brand new modern lightweights?