Hi,
Split skirt pistons run tight clearances compared to solid skirt
the split closes up as the piston expands preventing siezure as would happen with a solid skirt if the same clearance was used
My Ariel with a split skirt piston, has the same specified clearance as your A7
It was bored to 0.002in. clearance 30 years ago now
It has never given a problem and the piston is a lot larger than the A7
I would aim for 0.002in clearance
HTH
John