Comparative (Inversion)

Hello. When reading papers and books, I sometimes see the inversion in comparative sentences like below.

·Harvard undergrads, however, were unmoved. They generally give the impression of being far more supportive of their president than is the faculty. (This is from The Weekly Standard, March 7, 2005 )

Then, I want to know whether I can use could (and be) in the following way.

(If the Controlled Substances Act did not exist,)

1. drug overdoses could be responsible for more deaths than car crashes.

2. drug overdoses could be responsible for more deaths than car crashes could.

3. drug overdoses could be responsible for more deaths than car crashes could be.

4. drug overdoses could be responsible for more deaths than could car crashes.

5. drug overdoses could be responsible for more deaths than could car crashes be.

6. drug overdoses could be responsible for more deaths than could be car crashes.

Could you help me?

Thank you.