I think that it is going to depend on the rules that the shooters as well as the club are following. If the folks who are now using tiny cross sticks to shoot from prone positions are "liberally" interpreting the rules to gain an advantage then it is time to either change or challenge the rules themselves. If you go that route then be sure to be civil about it, don't just haul off and accuse someone of cheating as you will put everyone of the defensive right from the start. My experience using cross sticks comes from cowboy action shooting which restricted the use of them to a sitting position only, per the Cody-Dixon rules up until 2008 when they were changed, requiring all shots to be off-hand, unsupported.
Here's a link to replicating Billy Dixon's famous shot in which cross stocks were used in the seated as well as prone positions;
http://www.levergun.com/articles/bdixon.htmBPCR allows X sticks while seated and prone depending on the match;
5.2.1 Artificial Support for Black Powder Cartridge Rifle - Artificial support for Black Powder Cartridge Rifle only shall be in the form of approved design crossed sticks constructed of two wooden legs, no greater than 1 inch by 2 inches in thickness and width or 1 1/2 inches in diameter, and bolted or tied so that the two legs are hinged and capable of pivoting. The end of the legs may be equipped with spikes no more than 3 inches in length and no wider than the edge of the crossed stick. They may be inserted into the ground by hand pressure only to aid in retention of an upright position. This may be waived by the Match Director to fit local conditions. One layer of protective material may be suspended or inserted in the "V" of the crossed sticks to protect the rifle. All cross sticks will be certified.
5.8.1 Firing Position, Black Powder Cartridge Rifle - 200 meters - Any standing position without artificial support. The rifle will be supported by the hands and one shoulder. All parts of one hand must be forward of the pistol grip.
300, 385 and 500 meters - Any position, including crossed sticks, but excluding bench rest.
(a) A "crossed stick" position is one where the shooter is in a prone, sitting, kneeling or standing position with the barrel or forearm resting in or above the "V" of the crossed sticks in such a manner that no competitor or range personnel are endangered. See 5.2.1.