I also tow a 8.5x20 trailer behind my truck camper. Mine sits low with dropped torsion axles which makes towing and loading easy but you have watch driveways and unimproved roads. I am under 50' overall length (23' trailer and 25' truck/camper) and fit most pull through sites. Wider sites that are short allow me to double park in a 25x20 footprint.
Consider upgrading the axles to the heavier models for the same size. My trailer is over 3000 lbs empty and then I carry two vehicles, 84 gallons of water, 25 gallons of LPG and 17 gallons of gasoline which all make the weight creep up. Soon I will be installing solar and a battery bank in the trailer which will easily add 500 lbs by the time I'm done.
If I decide to go bigger in the future, I will go with a stacker (think of a double decker) instead of going any longer. Too may times we use the ferry system in our area that charges in 10' increments and I want the length to stay at 50' or less to keep charges down and campsites open.