Thanks. I drilled them out with a #80 bit and sharpend out the edges with a scalpel blade.
I liked the muted effect that was achieved by mixing a bit of "rust" into my usual "burnt iron" mixture of aluminium and flat black. (About 1 to 3, with 1 more part rust.)
Research has shown me that these early K5Y1 aircraft had the Japanese insignia applied as just a red "sun". It does not show up as well as later insignia would against the orange, but there you go; Historical accuracy, she is a harsh mistress.