Depends what anti-roll bar you use. Comptech doesnt require drilling but Progress ST GC and Skunk (I believe) do require it.

As for size issues try and stay around 22mm for a decent toss up between drivability and performance. GC and some other companies offer 25mm but thats quite a beefy bar and unless you are VERY familiar with the handling of your car Id stay away from it it is not meant for daily driving.