Thanks (again) David,
I'll talk to Peter at JP's re what he has lying around or could adapt. Stephen (son) has been there twice, but they have been closed the past couple of days.
The barrel is pretty good and unsleeved standard, no scoring but a bit of a top lip. I did think about taking a punt on a standard piston.
Thanks for the offer of your piston to copy.
The club spares list mentions a +10 with 'good compression' I'll ask what this means..
You never know, someone might have one in a box somewhere...
'51,'56 Squares, '48 VH, '27 Model C, R67/2, Mk IV Le Mans, '06 Super Duke and Ariel projects.