I'm posting this because in my past Google searches I found relatively little information on the subject. So for those of you interested in towing with your Legacy, it can do it. Last year I pulled a loaded U-Haul 4x8 trailer halfway across the country and it was a breeze. Size wise it fit the car well. This year I'm heading back the other direction but couldn't get a 4x8, all they had was a 5x8 within a days drive. It's not ideal as that extra foot in height makes it sit a bit above the car but there was no other choice. It ended up working out as the 5x8 is stuffed and there's no way everything would have fit in the smaller trailer. The car definitely sits a bit more squat though.
I've driven through the Rockies with both trailers and had no issues up or down. The 3.6 does well climbing the mountains and merging onto the freeway with a full load. Plus I'm still averaging over 20 MPG across 1800+ miles. Key safety points are properly loading the trailer and not driving too fast.
Mods on the car include an OEM 20mm rear sway bar, OEM CVT cooler, U-Haul trailer hitch and Michelin Pilot Sport A/S 3+ tires. Aside from the hitch I had everything installed after picking up the car from the dealer and long before I ever considered towing. But I'm glad I have them, particularly the transmission cooler.
Now queue up everyone saying to just rent a U-Haul truck and trailer the car. Also queue up everyone claiming my transmission will be found dead along side the road somewhere. All I'll bother saying about either is if everyone online was as smart as they claim the world's problems would be solved overnight. Often life isn't about doing something in an ideal way with limitless funds on tap. Sometimes you just have to do what needs to be done. So if you need to tow with your Legacy it can be done safely and economically.