Hello again!
I've made some tests based on the photo you have on page 7 (
https://forum.ww1aircraftmodels.com/index.php?topic=10771.msg199529#msg199529). When you zoom in on that it looks like only the D and 2 have white outlines. It also looks like the 6 sits right on top of the blue/white border, as does the 0 but on the white/red border.
It's doable, but it's a bit tricky and I would suggest painting it before you have attached the rudder... Take a look at these pictures of my test run and let me know if you would like to try and use my masks.
I copied my Camel rudder onto a piece of plasticard. Again from the image, it looks like the white band is slightly wider so I went with that. The painting is done in two stages. First you would paint white where I used red.


Then you remove the inner mask - this was what Richie was referring to - and then place the second mask inside the outerbox. One should wait longer so that the paint dries... I rushed this a lot, hence the paintlift on the D, but the 2 came out alright.




Take care!
Fredrik