I think most folks around here use the term snap and don't fully understand what the term means. A snap is a condition where one wing(or a portion of a wing panel) stalls before the other that causes an abrupt roll in the direction of the stalled wing. A snap-roll is a maneuver that uses this one-side-stalled condition to rapidly rotate the airplane around it's axis on purpose. If your plane does this and you didn't mean for it to then you have what the full size pilots call a departure from controlled flight.

With every airplane I set up one of the first tests I do is to apply full elevator at full throttle and see if the plane will track 3/4 of the way through a loop without departing. I usually find that I will get a departure while either entering the loop or at the top and sometimes it will get me at the exit but the throttle is usually reduced on the back side of the loop so if you depart there your really using too much throw. This ALWAYS has been the result of too much elevator throw. I land the plane, dail out some throw and repeat the test again and keep doing this till the plane will track through a loop at full power with zero departures. This becomes my low rate setting and I fly the plane there till I either lose it or sell it, whichever comes first.

The intersting thing is that most of the modern designs have such huge surfaces that they reqauire VERY little throw to get the job done effectively. I usually find that most planes have more than adequate elevator authority with as little as 10 -12 degrees. You also need to understand that ANY change in balance will affect this setting and you'll need to re-fly the plane and do the full-pull test again to make sure your plane will not stall and depart.

As for high rate set up that is a completely different animal and is another topic entirely.