Subaru Outback...how well does it tow a sailplane trailer?

I tested my 2010 Outback 3.6 automatic with a boxy metal trailer we use to hold our PW5. I just went a couple miles on a freeway and was getting blown around a lot by passing trucks. I've done a lot of towing and this felt quite unsafe. However, with a modern, low-profile glider trailer it should be fine. Before buying my OB, I spoke with a fellow who tows a Sparrowhawk very nicely, but then that's the extreme low end of the scale. So your results would be somewhere in between... it would be great if you could test your trailer with a friend's OB.