FWIW, pickup trucks are almost always allowed to autocross at SCCA events.
Sport Futility Vehicles are usually not, although it is at the discretion of the event's Safety Steward. I have seen an experienced driver allowed to run a Jeep Grand Cherokee.
I would think the Forester's distinction as the only 'mini-ute' which does *not* require a rollover warning sticker would help in this case, if required.
I'm not surprised to hear that that Forester was fast, it is not nearly as different from an Impreza as I thought. Basically, it's taller, and 200 pounds heavier. I wonder how different the suspension is.