Look at my signature below, I have a 30' trailer also and when I had put Goodyear Silent armour tires on the truck and aired them up to 80 psi, it was scary driving down the road compared to when I had the stock oem tires on the truck. I now have Good year dura tracs on the truck and all the handling is back to normal. My point is that the tires on the truck can make a world of difference reguardless of how it is loaded and connected sometimes. Proper loading as the others have mentioned is very critical also thoug. I hit 140 km/hr sometimes passing and it doesn't scare me with the trailer in tow. My truck is a dually and the tires still made a very noticable difference.
Gee I would have found it scary to air up the Goodyear's to 80psi without being in some kind of explosion proof cage :-laf never had much luck with Goodyear