When we had a TT it came with 4 jack stands...the type used on mobile homes.
I would get the trailer level side to side using blocks under the tires. Then unhitch and level front to back using the tongue jack. I would then lower the front until it was just unlevel and place the rear jack stands under the frame and adjust them until they were tight against the frame.
Next raise the front of the TT to level and place the front jack stands under the frame. Tighten them up against the frame and raise the tongue jack just a little to put more weight on the front jack stands.
The jack stands would support the weight of the TT and eliminate any bounce from the springs or tires. The TT was rock solid.
You can buy these type of jack stand online or at some of the independant RV Supply Stores.
Here's one supplier http://www.bandrstamping.com/LEVELING_JACKS.html