Something adjustable with minimal play and limited trigger travel, decent strap, adjustable for reach and trigger weight and travel. The other important issue is to find a solid consistent anchor, I always tended to find I struggled because I was trying to match 2 "rounded" surfaces against each other (back of hand on to corner of jaw bone),
And finally watch how much you are cupping your hand, especially under pressure people tend cup their hand more than normal and find that suddenly they can't reach the trigger the way they normally do !