John, your decision may have to come from comparing many only similar experiences. I brought my 16 home yesterday [pause for wild cheering and applause], behind a Toyota Highlander. The vehicle is rated for 2000# as is, 3500# with special gear --on the vehicle. With the boat empty and no motor(s), it pulled "like it wasn't there" (except for that infernal jiggling) --until I went to slow.
This Highlander that once stopped in less than its own length in city traffic, cycling the ABS three times, could not slow the boat much even at surprisingly high pedal pressure. I'm pretty sure the problem would be worse on the Subaru with brakes originally built for a lighter vehicle. Maybe both of us should see a Magic Tilt dealer about adding trailer brakes.