Thank you everybody!

Unfortunately I don't own an incident meter, I only use the meters of my two SRL (Nikon FG-20 (CW) and F100 (CW /Spot)). It seems that +0.5 should be a good compromise; I might bracket from there....

Ok, need to complete the Fomapan 100 roll on the F100 and load the Astia
I'll let you know!