I would no sooner trim the weedquard in a jig to make it shorter, than I'd take a pair of pliers to the hook to close up the gap. Despite what so many anglers seem to believe, long weed guards make hook setting easier, not harder. In fact, I have my casting jigs made with the weedguard extra long. Think of the weedguard as a lever. The longer the lever, the less force it requires to move it. The same guys who want to trim the weedguard down so that it barely reaches the tip of the hook are the ones who will tell you you need a wider gap hook gap, too. I contend that's mostly because their trimmed weedguard makes the effective hook gap smaller!
Why cut off the portion of a fiber weedguard that extends beyond the hook point? This part of the guard does absolutely nothing to interfere with hook setting. It's actually the section of weedguard closest to the head that most interferes with hookups, because of the way the material bends. The problem with fiber weedguards is that the material is uniformly flexible, so it flexes in an arc when pressure is applied to it. The "bow" of that arc ahead of the hook point makes the effective gap of the hook smaller. This situation is made even worse on many jigs because when they are painted, capillary action causes paint to wick its way up into the weedguard. When the paint dries, the section of the guard near the head is stiffer than the rest, causing the weedguard to bend farther from the head (and closer to the hook point), leaving more of the gap obstructed by the arc of the weedguard.
The best thing you can do to the weedguard on your new jig is to grab the it very close to the head and flex it back and forth several times as if you were trying to break it off. The idea is to create a weak spot, so that when pressure is applied to the end of the weedguard, most of the bending takes place down near the head. This lets the weedguard collapse and get out of the way, instead of flexing, and exposes more of the hook's gap. End result is more and surer hookups.