It's a matter of geometry....in order to get more extension, you need longer end-components but that's the opposite you need for the "low boy" setup. The compromise would be to use the A-A-B for most work and have a torsion box available that you can throw on lower supports when you need that accommodation for something you're assembling. It's easy to store a torsion box away in the sheet goods rack or against a wall somewhere.
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The most expensive tool is the one you buy "cheaply" and often...