I would be hesitant to use the corners as the frame could flex. I believe this is where most of the warnings come from. That and the basic scissor stabilizers provide almost no resistance to horizontal movement.
I would look at the 5th wheel auto level systems. It shouldn't be hard to adapt those to a travel trailer. Most include a set of stabilizers near the axles.
As long as the wheels are firmly seated on the ground (with the springs extending as you lift) normal blocking of the tires should work. I've never been comfortable when I see 5th wheels with one side completely off the ground. The legs are simply not structured well to resist horizontal movement.
