assemblies without identifier

I have an application where I use the assembly plugin to create a package file for computation software called octave.
It is just a file artifactId-version.tar.gz with a predefined folder structure.
The problem is that the assembly plugin doesnt do without an assembly identifier.
Then the result is something like artifactId-version-assId.tar.gz.
Strictly speaking, octave needs the first kind of name without assId.
My workaround is to copy xxx-assId.tar.gz to xxx.tar.gz
but then the install plugin fails expecting still xxx-assId.tar.gz.

My question is now whether it is possible to allow empty assid
in case there is a single assembly only.
This would solve my problem.
The other way to solve is, maybe to understand how the install plugin finds out what to install.
Does the assembly plugin pass any kind of information??
I cannot imagine.

Help, in any way, very much appreciated.