Don't most Subarus have a hitch weight
limit of 200 pounds? I think you'll likely exceed that. Also, the longer shank on the drawbar puts the ball further aft, increasing the lever effect and reducing towing stability.
Several forum members built custom racks over the battery/propane tank close to the shell. That would be a little better for tongue weight
and a lot better for turning and hatch clearance.
In my mind the best solution would be a roof mount system on the Forester. That way you can take the bikes somewhere away from camp to ride if desired.