'so cannot' is correct and usable in written English.
It is usually used when expressing a logical conclusion from a previous statement. Example: He had already eaten dinner, so he could not eat any more.
The antagonistic control problem is not convex, and so cannot be efficiently solved.
Some do not have seeds and so cannot be stored on Svalbard.
They also tend to lock into long-term contracts and so cannot increase prices each year.
But simply saying so cannot be the end of the discussion.
Stealth planes absorb the radar signals and so cannot be located in this way.
These structures are, however, quite simple and so cannot be said to determine the content.
But Americans do not know about its rulings, and so cannot challenge them.
These rights have no paper value and so cannot normally be sold to developers.
But these require dissecting the cells, so cannot analyze living, circulating cell populations.
And a growing number of those patients have no insurance and so cannot pay.
But most people do not know what to listen for, and so cannot reconstruct the thought.
