My brother just dragged a Hobie Tiger from one side of Australia to the other and then back again in a Suby Forrester and it ran fine (7000 mile return trip). Fuel economy wasn't great though.

Just another tip - You have looked at your tyres, bearings etc which is great. Also look at your trailer springs and "U" bolts. I have seen several break (usually caused by rust) on long trips over the years which is silly because they are really cheap and easy to replace.

Michael