The other day I posted pics of a low table I designed for easy breakdown/setup and transport. Here is the tall version of that table. It uses the parts from the low table, the low table top as the high stretcher and the low stretcher as the high table top. 60 x 90cm leg pieces were added from another sheet of plywood.
After assembling, the table is quite stable, though it does rock a bit because of the plywood thickness. In spite of the rocking, it is very hard to unbalance.