Piston clearance in bore, 3hp CS1

[donmilne]

Greetings Lister afficonados.
I am overhauling a CS1 3HP and in the process having the barrel bored + 0.040"  to remove a nasty lip at the top of the stroke.
I have a new Cast iron piston also + 040" to fit, the question is what clearance should be given between the two parties?
I have seen a clearances in the range of 0.001"  to 0.002" per inch of bore suggested which would approximate to 0.004' to 0.008"for this motor.
Any suggestions would be appreciated.
Don Milne   Dunedin      NZ