How heavy is the travel trailer, and what's the tongue weight? Most people who tow travel trailer use a weight distributing setup to properly redistribute the tongue weight rather than just rely on the shocks. Personally I use the Reese Dual-Cam system which is weight distributing and sway control all in one set of parts.
I know with my 6500-6600 lbs of towed weight and 800-900 lbs of tongue weight that the stock self leveling shocks can't ever lift the rear level. But the spring bars of the Reese when set up properly get everything perfectly level then the air shocks just fine tune the final inch or so of height. The bonus is far better towing stability, and no modifications to tow vehicle.