I guess I'm in the minority, but I don't think putting the QB under center does anything, and in fact I think it makes it worse. Sam is effective because he hits the line, not because he pushes into it or tries to crawl over it. Taking the sneak under center takes away all forward momentum, and it only adds about a second to the play - which also removes the time for your blocker to push forward. If he can score by pushing forward from a standstill, he can score rushing straight ahead a half-second later.
If your o-line does the job, there is no advantage to lining up under center, and if it doesn't do the job, there's the disadvantage of a QB who has nowhere to go if the line gets pushed back and no forward momentum.
The fact is, we didn't execute it in the first half. We came right back to it in the third quarter and punched it in. Formation was not the issue. Poor execution along with a dropped pass and a fresh and fired up LSU front was the issue.
If you noticed the primary difference between Sam scoring in the third quarter and not scoring when his knee hit in the first quarter, that the second time, Sam turned his back to the play and pushed with his legs, knees pointed up. He wasn't going to let his knee accidentally hit the ground that time around, and he drove himself into the end zone.