you need an AddonSocket on the trailer
<Socket Names="yoursocketname" Offset="(0; 0; 0)" />
in LoadArea you have to define the areas in which you are able to pack the load (obviously) in which the green dots need to be
and define the type of logs the trailer is going to be able to pack (in this case i'll use long logs, so LongLogs, can be ShortLogs or MediumLogs too)
Min="(0; 0; 0)"
Max="(0; 0; 0)"
and if you want to use a custom mesh for logs (which i really recommend, the stock log meshes have very weird shapes) this is what your XML in classes\trucks should look like
<Body CenterOfMassOffset="(0; 0; 0)" Mass="0">
<Constraint Type="Fixed" />
<GameData LoadPoints="0" ManualLoads="0">
<RequiredAddon Types="your trailer addon name" />
<RequiredAddon _inheritRemove="true" />
<InstallSocket Type="yoursocketname" />
<_parent File="load_logs_long" />
LoadPoints defines how many points you get towards the lumber mill when you unload, ManualLoads defines how many logs you need to load manually onto the trailer to be able to pack the load
i recommend adding the trailer to RequiredAddon so you won't be able to load logs unless you have the trailer attached
InstallSocket Type is the same socket you defined on the trailer obviously
_parent File defines the parent file for your logs that will be used by the game for the other needed information, i recommend using the one that fits the size of your load the most. you can find the other names in the Media.zip.
also @Spun i heard nix say in the stream yesterday that he's trying to figure out custom log meshes for the log jammers, so maybe this is helpful to you too
you could play background music while playing on the xbox media player on the xbox360 (via USB stick or media server), it would be really stupid if they removed that feature on the xbox one. if anything they should have further implemented it with spotify or other music streaming apps