A 0.5 degree increase in camber only requires a change in length of 0.0769 inches of a suspension component that holds the wheel at a desired angle.
There are many ways to change the length. It could be an obvious slot as reported to have been done by Danny. You could also adjust many different parts of the sub frame, the knuckle or lower control arm.
Currently there are not any dimensions on these parts in the rules so you have to compare the part in question to a new one. Sure a slot is obvious- but will you visually see 0.0769 inches on a sub frame when compared to a new one? Would you see a 0.5 degree bend in a knuckle? Who actually has a new subframe (with a part number and in a factory bag) at a race to compare it to? How do you prove it was not tweaked due to contact? If the cam adjustment slots are worn and the upper control arm mounting bolt hole are worn how do you prove it was modified not wear from someone driving with the bolts lose when it was a street car for 200,000 miles? So now you might say publish dimensions and measure. What are the tolerances on each part? How precise can you measure a sub frame? Is the gain some want smaller than the tolerance stack up and measurement error?
Point is if you are cleaver and want to cheat on camber you can- this is not new. There are many ways it can't be measured and proven Danny simply brought it to everyone's attention. Why not take the cheat away, level the playing field, reduce cost and time spent? A 0.100 inch slot is almost free takes just a few minutes and removed any advantage (real or perceived). This is what my letter will ask for.
Some very good points but I don't like the slotting method as the bolt will probably move in the hole under racing stress unless it's bushed somehow.