I have used a Larsen 220 MHz through-glass antenna for the past 12 years and it works fairly well. However, it does not compare favorably to a 1/4 wave antenna installed in my NMO mount, so that should tell you something.
Have you considered an NMO mount installed under the lip of the Outback's rear hatch? I did that with a 2002 Subaru Outback and it worked great. I now use the same mount on my Jeep with excellent results on 6M, 2M, and 440 MHz. To establish a good RF ground I did drill one small hole under the hatch overlap but nothing is visible on the exterior of the vehicle. It works much better than my through-the-glass mount and I can still drive into the garage without any contact between the antenna and the garage door.
Whatever you decide, good luck with the new installation!--
Politicians are the only people in the world who create problems and then campaign against them. (Charlie Reese)