Apologies for keeping on reviving this post!
Sunday was a nice day to be working outside, so took off the tank again and was able to check the air filter.
Luckily the 'clean' part of the air box was still clean, the airfilter sits in a lower part and so the oil collects down there. At the bottom is a small hole for the oil to get out and that's why it had gotten out over the engine.
So my own conclusion is that overoiling an airfilter is definitely possible, probably not as dangerous as I thought at first. Just very annoying it you've been cleaning before..
While being down there I've fitted the replacement stick coils, so thats one less worry as well.
I also have gotten round to installing a radiator guard, since in sweden the municipalities use some kind of gravel in the winter to counter snowy and icy roads. The fit was not perfect, needed some washers but I think the result is nice!