Gareth, you don't have to crank up each half hitch itself, the idea is to set the entire knot after the half hitches are done (just keep them firm)! You gotta remember the knot is designed to slip slightly (very slightly) in order to bite into the leader.
Luke, I have had one or two FG's "back out" without burning the end of the leader over, obviously not tightened enough. This has followed repeated casting (Ie loading and unloading the line) without hookups (more intense pressure). This hasn't happened to me with the leader end burned over.
The way the knot is structured, if the first wraps on the leader are pushed toward the half hitch end of the knot (which is the direction of pressure the guides can exert on the wraps during casting) the knot can slide. I've noticed, the longer the wrap section that is tied, the more prone these first wraps are to sliding, due to the fact that friction at the hitch end of a 'long' knot prevents the first wraps from being tensioned by the tensioning process!
As such, I've found a 'long' knot, potentially less reliable than a short knot (I preface that by saying an innadequately tensioned 'long' knot)!
For what its worth, I know tie about 1/2 inch of wraps in PE6 (3/4 inch in PE8), 8 full hitches (one way), 6 mainline hitches (alternating) and burn the leader end and braid tag (the braid tag is just to stop it fraying) - haven't had any issues since!