Mine is clipped in nice and tight, there is definitely a bit more poke from doing it and it inspires my heavy foot with the roar. It's still subtle enough to cruise by unnoticed, especially near home where you don't want to be labelled as a 'boy racer' especially as I'm not a boy now
I didn't have to slit it, just sit it on something sturdy and get about 3mm in on one side, then squeeze towards the other side to get that side in, then slowly push harder to get it all the way in.
I'll continue reading down the 'must do mods'

- I have some s3 callipers so need some pads to go in them, on the shopping list for this week!