This document has been overcome by events. On 27 Sep 2019, the N42PA amended the rules by clarifying proper domino placement (Rule 8) and defining "talking across the table" (Rule 17). The new rules are posted HERE.
The original N42PA rules, archived in 2015, state the following:
"II.4. Dominoes shall be lined up in two rows with three in the front (near the player), and four in the back (near the table's center)." (4-3 or 3-4 placements were not optional to preclude signaling opportunities. - PP)
"IV.15. Players shall not provide any physical cues or verbal statements (talking across the table) to their partner." (No further definition of "talking across the table" was provided. - PP)
"8. Dominos must be placed in a 4-3 or 3-4 format once you draw from the shake." (This allowed one of the options to be a signaling opportunity. One 42 club rules say the first opted choice must be used for the remainder of hands in a game/tournament. - PP)
"17. Any physical signals or cheating of any kind will not be tolerated ... (examples cited)."
(This helped me decide on a contest winner. The winning entry covered private pre-game indicating agreements between partners, including domino placements. - PP)
The contest winning submittal pretty much covers "problematic pre-conversations." The other issue, culturally learned indications, still needs to be addressed. Unwitting traditional players who use questionable indicating practices need to know if their learned methods are acceptable in sanctioned tournament competition.
If the leadership does not address the issues, then Texas 42 will continue to be primarily a regional fun game to play in Texas and its bordering states. Social players feeding into sanctioned tournaments will have to decide for themselves what constitutes fair playing practices in sanctioned tournaments. (Hopefully, sanctioned 42 tournaments will expand beyond the borders of Texas and New Mexico.)