Hi Kiwi!
I got JPs in the A7 SS, with no negative things to report whatsoever! I fitted them with a clearance of 3.15 thou (8/100mm), for the larger bore A10 you might want a tad more, around 4 to 4.5 thou I'd say.
The need for larger clearance is not necessarily a sign of inferior material or greater thermal expansion, the main reason is that the JPs don't have slotted skirts for expansion control. The larger clearance might cause some more noise when cold (although I could never notice any undue noise, unless the pistons and bores are REALLY worn). But otoh a solid skirt piston is substantially stronger than its slotted counterpart. Slotted pistons in Norton Commandos are known to fall apart at high revs regularly, owing to the high piston velocity of the larger capacity engines.
At the risk of repeating myself: If you want something really really good and can afford them, go for a set of forged Wisecos from Cake Street Classics!
Cheers, Markus