Can't shoot yet, still recovering from surgery but I can type
Gaps between KZ and plate are common in HFT owing largely to the distance between pegs (i.e. fairly straightforward shot seen straight on made difficult by forcing position together with the "50% obscured by twigs, trees, etc" rule). I don't see why FT should ever have that problem unless the target has moved (often because it isn't in firmly or up a tree and moved usually because someone yanks on the strings too hard. Rather than stop the shoot wouldn't it be much more simple for a marshall to have the use of a spotting scope and tripod? 60x zoom with a huge objective is clear as anything out to 50m. Easy to see a gap and if someone pulls on the string you can easily tell if the target is moving (i.e. then the whistle can be blown).
If anyone wants to quibble about little fingers then good luck because thumbhole stocks, custom grips, etc all offer support to some extent. Which is odd since the trigger hand should be relaxed and just there to provide a trigger finger. If the hand is gripping then a tendon will push the aim off on long shots.
I used to shoot prone with a sling - super stable - but very rare to see a course where FT can be shot prone. Using a sling kneeling or standing is more trouble than it is worth and you have to push the rifle up against the sling since having the sling supporting weight downwards is not permitted. Slings make sense when the firing position is the same every time i.e. 3P but other than prone (even then it can be hopeless) they are no help.
To break a bad habit of "gripping" with the trigger hand I started using the middle finger rather than index finger - tendon in a different place and it keeps the grip loose.
Have fun in the Winter leagues (all I can do is discharge a few dry shots safely just to keep the regulators happy - having just got them sorted).