Common Sense
First and foremost, common sense should be used at all times on littlewhitey's SA-MP Server. If you know, believe or even have a suspicion something you are doing is wrong and could get you punished then you should not be doing it - if in doubt, contact a member of the team for more information.
This is the main statement you should keep in mind when modding. We officially do not support any mods, so keep an eye on the possible advantages a mod could give to you in comparison to players who don't have it. You should avoid the following things:
Bouncing/JumpingIf a car model is longer or shorter than the original SA one it replaces, the sa-mp server sync shows an effect that is known as 'bouncing'. Your car will then permanently switch beetween two positions, and show some meters ahead, then again some meters behind your actual position for oher clients.
This happens because the sa-mp sync uses two values to sync the car on the server, the front and the rear.
Example: Your modded car is longer than the original one. The server syncs the front, the rear is some meters beyond the actual rear position of the original car. When then the server syncs the rear, the long rear of your car will be placed at the rear position of the original SA car, causing the front to be placed forward beyond the front position of the original SA car, causing your car to 'bounce' beetween those two positions.
Same goes for the height, so your car may end up stuck in the ground for others.
LagSome car mods have many details and use many polygons to render, which might affect your performance. Excessive lagging while having a good ping can ground a lag manipulation suspicion, so make sure the car doesn't lower your fps.
OpcodesSome mods have special features, tuning parts, etc. that again depend on other mods. If you don't have all the files a car would need to work installed correctly, you may cause runtime exceptions within yur client, known as 'Opcodes'. Those normally show in light blue text in your chatbox and have the potential to crash your game.
If this happens often, you'll have to rejoin often. And if you rejoin to often, you might exceed the anti-bot join limit, and the antibot will ban you. Those bans can only be resolved by management members, so be careful when testing your mods.
Physical AdvantagesThe handling of a car within the SA physics engine is not only dependent on it's handling.cfg code, but also on the shape of the .dff mesh.
Thus some car mods don't really handle well with the sa engine, so they come with custom handling lines that would compensate those issues. In the new sa-mp versions though, the handling.cfg code and some other .cfg's are not loaded client-sided anymore, but serversided to prevent easy hacking through editing of the files. Thus you should always test any car mod, for once if the tires fit in size, then if it still handles well, if all the tuning parts work without crashing the game, and lastly if the mod handles actually better than the original car, because that would be an unfair advantage that could lead to a ban.
I hope this helps, also don't forget to make backups!
VC-MP: 
