Thanks for the feedback.
The boards are made from expanded polystyrene (the kind used for house insulation and such) and the carbon rods which are sharpened in one end is poked directly into the boards. The holes seem to close themselves again a bit. The boards are amazingly resilient being more than 100 games and 16 years old.
As to the visibility of the rods, we haven´t really felt bothered by them in real life. I think they look more intrusive on the pics than they are experienced - probably due to camera angles (often top-down and very close to the rods and planes) and that the planes are very small in 1/350 scale = about 2 cm wing span). The rods are actually only 1,5 mm wide.
But I really like the idea of having the rods in some less noticeable color such as a light sky grey and i think I will make a spray paint test on a couple to see the effect and if the paint will stick.
Here is a more normal player eye view: