you don't seem to understand forces
The saw horse configuration would have no problem supporting that weight as many can do at present ...assuming the legs can't fold outward.
The extended configuration is the issue. All the stress from a load in the center will be concentrated at the hinges that allow the legs to fold, even if the center bar is strong enough to support the weight without bending.
Without knowing the reason or application for the folding legs, the cost of making the joints strong enough will likely outweigh any other advantages. It's an interesting concept, but not practical in real world terms.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)