Trailer configuration mod

I was looking to modify some trailer addon to have an attachment point to have an other trailer attached behind,i tried to edit the .xml of a trailer without much success.
I remember reading it was impossible to do so but i didn't find that topic again.
-is it possible?
-if not what are the current restriction?

Here a snipet of the xml
<WinchSocket Pos="(-9.298; 0.727; 0.609)" />
<WinchSocket Pos="(-9.298; 0.727; -0.609)" />
<WinchSocket Pos="(-6.519; 1.173; 0.662)" />
<WinchSocket Pos="(-6.519; 1.173; -0.662)" />
<WinchSocket Pos="(-2.162; 0.82; 0)" ParentFrame="BoneHandle_cdt" />
<InstallSocket Offset="(-2.047; 0.816; 0)" Type="KamazTrailerCart" ParentFrame="BoneHandle_cdt" />
<AddonSockets _inheritRemove="false" />
<Socket Names="KamazTrailerCart" Offset="(-7.047; 0.816; 0)" />

last edited by Raphael

As far as I know, it is not possible to add an addon to an addon. There are a few trailers out there that have a trailer attached to them but those two trailers are one addon and can not be separated.

Actually i saw russian player do that in front of me a while ago but he probably had a workaround either through editing live memory or something else so,it's not completly out of possibility.
There is just something somewhere who need to be done.
What i m interested in is where the limitation are either you can still do some xml editing but will not pass the file check or is it something in the executable who need to be altered.