On what it means to "fling" the sword
There are two good descriptions of this in an forum thread hosted by the Order of Seven Hearts
Flinging, as Fabris uses the term, applies to extending your arm as quickly as you can–think of a boxer’s jab. While this is good technique for boxing, it is pretty bad for Rapier (and any later Italian swordsmanship, for that matter). While the extension is very fast, it is also very weak and difficult to control. That is, once you’ve started the ‘fling’, you can’t really alter your initial motion, nor can you respond to any sensations on your blade in a timely manner.
The correct technique is to extend fully (obviously, Fabris’ extended guards start this way) and then the point is driven forward an into the target with the lunge, thus it is your body and not your arm that provides the impetus to the thrust.
Actually, this is a very good question, because ‘flinging‘ is pretty much where most of the community is. While it is what comes instinctively (since we naturally want to deliver attacks as quickly as possible), it is not the most effective method of attacking–a calm and experienced fencer knows that he only need move fast enough to perform his action within the length of his opponent’s tempo.
— Steven Reich
Flinging a thrust is my translation of "lanciare la punta," which consists of performing a thrust by means of a vehement arm-extension, with no support of the body or feet when the thrust arrives on target.
Lanciare la punta, or "flinging" went in and out of fashion in Italian fencing. In the Bolognese style, when two or more consecutive arm-extension thrusts are often performed in rapid sequence, the masters actually instruct you to withdraw the arm well between one and the next.
The apparent widespread use of this technique in the 16th Century may be the reason why Fabris–who truly heralded a radically new style–spends time and ink warning you against it.
We could argue whether a standard Classical riposte in opposition with no lunge is an arm-extension thrust; but for sure, what it does not have as far as poor elements is the withdrawal of the arm that would turn a fencer into a "pitchforker" (forconatore), as for example would be the case if the action was feint, withdraw the arm, disengage, thrust.
— Tom Leoni
More on this when I write my notes on Chapter 14, wherein Fabris extols the virtues of guards consisting of an extended sword.