[EngiNERDBK]

The way I see it, and correct me if I'm wrong, the rules state that you cannot touch another ROBOT. The rules also seem to acknowledge that the trailer is NOT part of the ROBOT by using phrases such as "The ROBOT and the TRAILER." So I believe that if you can somehow create a small enough ROBOT, with an appendage that fits inside the given space, you can touch other teams' trailers without grabbing or climbing the trailer and still be legal.
I also believe that this applies to your own trailer, if you can still fit into the space requirements.