No comment on the whether or not you should post a trailer here, because I'm not a host in this forum.
You're probably right about the poor visibility in that place, but I think the Screening Room is a nice idea in general. I think it just needs a bit more advertising. Besides, a trailer posted here may get more visibility here at first, but only for a short while. After which it will start sinking into oblivion fast, whereas in the Screening Room it'll stay relevant longer.
In other words, the simple solution to the eyeball dilemma would be more effort from both the administrators/hosts and the users in this forum to make the Screening Room more popular. Talk about it, move unrelated clips to it, maybe even link to clips inside it, compose songs about it and so on, so that people will notice its existence and start flocking there more often, and eventually automatically.
Well, just my 2c.