Tomáš always says that anything below 30 degrees is fine.
A few secs of hovering will anyway reset the horizon (unofficially).
The thing about "not tilting after initialization" is more something like "
don't lay the heli on its side for one minute while putting on canopy, then immediately take off and try Rescue". There was somebody in the past acting like that and then complaining Rescue was not climbing straight.
Personally, for my piece of mind I built a couple of leveling platforms which I use so that the only tilt is the natural heli stance, which is always a few degreees only. Rescue ALWAYS worked perfectly for me, 100%. And the last platform even looks cool