The Movecraft plugin generates disproportionate amounts of lag for ships with large cross-sections. Build your crafts and vessels to be short, thin, and long to reduce the produced lag. Obviously, there will be legitimate reasons to make fat and tall crafts, and that is ok.
Ships should be no less than twice as long as they are wide, and no more than eight times as long as they are wide.
Exceptions to this rule may be applied in a few cases. In general, the Admin Team will only consider "significant" portions of a craft. An informal "rule-of-cool" exists that permits some design violations for the sake of having an awesome looking airship. The purpose of this rule is generally to prevent the creation of excessively trolly combat crafts, so non-combat crafts can be considered provisionally exempt from these restrictions.
The above rule does not apply to land vehicles, airskiffs, and submarines.
A TNT cannon may not fire more than 36 projectiles/30 propellant every 4 redstone ticks. Your firerate and gunpower will be limited by the Overheat mechanic.
Flak weapons are provisionally legal weaponry. Flak guns are guns designed to explode at redstone-designated points in their flight path, near or on targets. They are generally also designed to produce large clouds of TNT. You are allowed to make such weapons, as long as they do not produce substantially weaponizable vertical redirection.
Autocannons are provisionally legal weaponry. Defined as any TNT cannon with a firing cycle less than 4 seconds.
Boarding actions are legal, and you are permitted to board enemy vessels and engage in combat that way.
You may not use enderpearls or chorus fruit to teleport onto enemy ships,
You may not place blocks on enemy ships in order to obstruct their movement.
You may only place blocks in the path of enemy land vehicles in the course of building fortifications. This notably does not include encasing an enemy tank in obsidian.
Ship ownership is especially important, and determines who has a legal right to modify, control, and copy ship designs. Ships always originally belong to whoever constructs them. Ships constructed by multiple players are considered owned equally by those players, save for verifiable evidence of a contract that defers the ship’s ownership to a single player. For example, 5 players build a ship for 1 other player, under contract that after construction, the ship belongs to the 1 other player.
Ships may be stolen in combat, or from ports. You cannot dissect/schem a ship until you have successfully stolen it and brought it to neutral or friendly port.
Ships sold become the possession of whichever player paid the asking price as agreed to by both parties prior to the transfer of funds.
Ships can be legally seized by Port Authority in a Town. A Town may disallow individuals permission to remove ships from their town by the Outlaw system, and can therefore hold a ship hostage from criminals or whomever, for an indefinite period of time. However, the Town or Nation that seizes said ship does not acquire ownership of said ship, and may only hold it, but cannot destroy, copy, or otherwise perform any action limited to the ship owner.
Ship engines (redstone blocks) must be placed at the opposite end of the direction the ship is intended to cruise. They must be contiguous and unobstructed out the rear, although they may be covered by blocks designed to mimic grates, vents, rudders, and propellers (subject to admin discretion). Ship engines may not be placed in more contiguous clusters than the ship’s block count divided by 1000. (A 5000 block ship can have 5 engine clusters).
Vehicles require tires that must be in contact with the ground, with no other requirements. For a single tire that is more than a 1x1 block, only the bottom of the tire must contact the ground. The tire can only be as tall as the tire length in contact with the ground.
Smokestacks -- campfires used as heat dissipation -- must allow their smoke to reach the sky from the funnel. They may be covered by blocks if they permit smoke to pass.
Please note that completely obstructing your campfires with blocks will reduce their heat dissipation to zero.
Glow lichen must be internal.