it doesn't do too bad..... We normally do short trips to our local ramp and that is about it. Farthest we tow it is loto from MN. It's got the 8.1 gas so although it is not alot of power, it has enough to get you around just fine. The trailer has electric over hydraulic disc brakes, and the boat is only about 10k dry. It seems to have a fairly sufficient amount of stopping power when we've needed to use it. Trailer sway isn't much of an issue unless it gets really windy. Just keep it under 70mph or so.
I think you'll do just fine with your duramax and 35 Fountain.