besides ben, i know rik hinton shoots hill style longbows three under exclusively and has racked up some impressive kills.
all bows and archers are unique to some degree. all stick bows will work well if you allow them to fit you and not the other way around. you will hafta do some testing and trialing to make your shelton work its magic best. hopefully, the bow was tillered for 3fu and not split finger.
and of course your arrows - arrows are far more important than the bow, and hopefully yours are reasonably matched to both your bow and you.
how you address the bow grip is one major key. there are more than a few good ways to do this, try them all and find the one that's most consistent for you (not for me or them). i believe that with any bow type and any bow handle shape, there must be one single pressure point of contact, a "pivot" point. for most archers, this is between the web of the thumb and forefinger, somewhere on the fleshy pad of the thumb (refer to fred asbell's latest book on advanced instinctive shooting for bowhunters).
the bow is never ever gripped tightly, the thumb and forefinger tips touch and keep the bow from falling out of my hand, there is zero pressure on the palm or fingers. my bow hand is angled - this allows me to hit the same pressure point consistently and rotates my arm out and away from the bowstring. i never have a need for an armguard ...
not how i do it (full grip) .......... versus .......... how i do it (single pressure point grip) you want the nock to lightly grip the center serving, never not too tight.
your nock point height is for arrow up/down porpoising, and your shelf plate distance from center setting and the arrow's spine is for left/right.
with any manner of string grip, it's the finger that touches the nock that must do the lion's share of holding the draw weight. with 3fu, the ring finger just goes along for the ride - this is true for all three finger string grips.
the rest will be in your form - how you draw the bow, where and how you anchor, and if you are using your back muscles to constantly "push pull" as you aim and release. form is literally everything, in the final analysis.
good luck, keep at it - you have a fine bow, now it's up to you to unlock its inherent consistent accuracy.